(API Change) Improve graphics API consistency

Summary:
- Prefix all graphics subsystem names with gs_ or GS_
- Unsquish funciton names (for example _setfloat to _set_float)
- Changed create functions to be more consistent with the rest of the
  API elsewhere.  For exmaple, instead of
  gs_create_texture/gs_texture_destroy, it's now
  gs_texture_create/gs_texture_destroy
- Renamed gs_stencil_op enum to gs_stencil_op_type

From:                            To:
-----------------------------------------------------------
tvertarray                       gs_tvertarray
vb_data                          gs_vb_data
vbdata_create                    gs_vbdata_create
vbdata_destroy                   gs_vbdata_destroy
shader_param                     gs_shader_param
gs_effect                        gs_effect
effect_technique                 gs_effect_technique
effect_pass                      gs_effect_pass
effect_param                     gs_effect_param
texture_t                        gs_texture_t
stagesurf_t                      gs_stagesurf_t
zstencil_t                       gs_zstencil_t
vertbuffer_t                     gs_vertbuffer_t
indexbuffer_t                    gs_indexbuffer_t
samplerstate_t                   gs_samplerstate_t
swapchain_t                      gs_swapchain_t
texrender_t                      gs_texrender_t
shader_t                         gs_shader_t
sparam_t                         gs_sparam_t
effect_t                         gs_effect_t
technique_t                      gs_technique_t
eparam_t                         gs_eparam_t
device_t                         gs_device_t
graphics_t                       graphics_t
shader_param_type                gs_shader_param_type
SHADER_PARAM_UNKNOWN             GS_SHADER_PARAM_UNKNOWN
SHADER_PARAM_BOOL                GS_SHADER_PARAM_BOOL
SHADER_PARAM_FLOAT               GS_SHADER_PARAM_FLOAT
SHADER_PARAM_INT                 GS_SHADER_PARAM_INT
SHADER_PARAM_STRING              GS_SHADER_PARAM_STRING
SHADER_PARAM_VEC2                GS_SHADER_PARAM_VEC2
SHADER_PARAM_VEC3                GS_SHADER_PARAM_VEC3
SHADER_PARAM_VEC4                GS_SHADER_PARAM_VEC4
SHADER_PARAM_MATRIX4X4           GS_SHADER_PARAM_MATRIX4X4
SHADER_PARAM_TEXTURE             GS_SHADER_PARAM_TEXTURE
shader_param_info                gs_shader_param_info
shader_type                      gs_shader_type
SHADER_VERTEX                    GS_SHADER_VERTEX
SHADER_PIXEL                     GS_SHADER_PIXEL
shader_destroy                   gs_shader_destroy
shader_numparams                 gs_shader_get_num_params
shader_getparambyidx             gs_shader_get_param_by_idx
shader_getparambyname            gs_shader_get_param_by_name
shader_getviewprojmatrix         gs_shader_get_viewproj_matrix
shader_getworldmatrix            gs_shader_get_world_matrix
shader_getparaminfo              gs_shader_get_param_info
shader_setbool                   gs_shader_set_bool
shader_setfloat                  gs_shader_set_float
shader_setint                    gs_shader_set_int
shader_setmatrix3                gs_shader_setmatrix3
shader_setmatrix4                gs_shader_set_matrix4
shader_setvec2                   gs_shader_set_vec2
shader_setvec3                   gs_shader_set_vec3
shader_setvec4                   gs_shader_set_vec4
shader_settexture                gs_shader_set_texture
shader_setval                    gs_shader_set_val
shader_setdefault                gs_shader_set_default
effect_property_type             gs_effect_property_type
EFFECT_NONE                      GS_EFFECT_NONE
EFFECT_BOOL                      GS_EFFECT_BOOL
EFFECT_FLOAT                     GS_EFFECT_FLOAT
EFFECT_COLOR                     GS_EFFECT_COLOR
EFFECT_TEXTURE                   GS_EFFECT_TEXTURE
effect_param_info                gs_effect_param_info
effect_destroy                   gs_effect_destroy
effect_gettechnique              gs_effect_get_technique
technique_begin                  gs_technique_begin
technique_end                    gs_technique_end
technique_beginpass              gs_technique_begin_pass
technique_beginpassbyname        gs_technique_begin_pass_by_name
technique_endpass                gs_technique_end_pass
effect_numparams                 gs_effect_get_num_params
effect_getparambyidx             gs_effect_get_param_by_idx
effect_getparambyname            gs_effect_get_param_by_name
effect_updateparams              gs_effect_update_params
effect_getviewprojmatrix         gs_effect_get_viewproj_matrix
effect_getworldmatrix            gs_effect_get_world_matrix
effect_getparaminfo              gs_effect_get_param_info
effect_setbool                   gs_effect_set_bool
effect_setfloat                  gs_effect_set_float
effect_setint                    gs_effect_set_int
effect_setmatrix4                gs_effect_set_matrix4
effect_setvec2                   gs_effect_set_vec2
effect_setvec3                   gs_effect_set_vec3
effect_setvec4                   gs_effect_set_vec4
effect_settexture                gs_effect_set_texture
effect_setval                    gs_effect_set_val
effect_setdefault                gs_effect_set_default
texrender_create                 gs_texrender_create
texrender_destroy                gs_texrender_destroy
texrender_begin                  gs_texrender_begin
texrender_end                    gs_texrender_end
texrender_reset                  gs_texrender_reset
texrender_gettexture             gs_texrender_get_texture
GS_BUILDMIPMAPS                  GS_BUILD_MIPMAPS
GS_RENDERTARGET                  GS_RENDER_TARGET
gs_device_name                   gs_get_device_name
gs_device_type                   gs_get_device_type
gs_entercontext                  gs_enter_context
gs_leavecontext                  gs_leave_context
gs_getcontext                    gs_get_context
gs_renderstart                   gs_render_start
gs_renderstop                    gs_render_stop
gs_rendersave                    gs_render_save
gs_getinput                      gs_get_input
gs_geteffect                     gs_get_effect
gs_create_effect_from_file       gs_effect_create_from_file
gs_create_effect                 gs_effect_create
gs_create_vertexshader_from_file gs_vertexshader_create_from_file
gs_create_pixelshader_from_file  gs_pixelshader_create_from_file
gs_create_texture_from_file      gs_texture_create_from_file
gs_resetviewport                 gs_reset_viewport
gs_set2dmode                     gs_set_2d_mode
gs_set3dmode                     gs_set_3d_mode
gs_create_swapchain              gs_swapchain_create
gs_getsize                       gs_get_size
gs_getwidth                      gs_get_width
gs_getheight                     gs_get_height
gs_create_texture                gs_texture_create
gs_create_cubetexture            gs_cubetexture_create
gs_create_volumetexture          gs_voltexture_create
gs_create_zstencil               gs_zstencil_create
gs_create_stagesurface           gs_stagesurface_create
gs_create_samplerstate           gs_samplerstate_create
gs_create_vertexshader           gs_vertexshader_create
gs_create_pixelshader            gs_pixelshader_create
gs_create_vertexbuffer           gs_vertexbuffer_create
gs_create_indexbuffer            gs_indexbuffer_create
gs_gettexturetype                gs_get_texture_type
gs_load_defaultsamplerstate      gs_load_default_samplerstate
gs_getvertexshader               gs_get_vertex_shader
gs_getpixelshader                gs_get_pixel_shader
gs_getrendertarget               gs_get_render_target
gs_getzstenciltarget             gs_get_zstencil_target
gs_setrendertarget               gs_set_render_target
gs_setcuberendertarget           gs_set_cube_render_target
gs_beginscene                    gs_begin_scene
gs_draw                          gs_draw
gs_endscene                      gs_end_scene
gs_setcullmode                   gs_set_cull_mode
gs_getcullmode                   gs_get_cull_mode
gs_enable_depthtest              gs_enable_depth_test
gs_enable_stenciltest            gs_enable_stencil_test
gs_enable_stencilwrite           gs_enable_stencil_write
gs_blendfunction                 gs_blend_function
gs_depthfunction                 gs_depth_function
gs_stencilfunction               gs_stencil_function
gs_stencilop                     gs_stencil_op
gs_setviewport                   gs_set_viewport
gs_getviewport                   gs_get_viewport
gs_setscissorrect                gs_set_scissor_rect
gs_create_texture_from_iosurface gs_texture_create_from_iosurface
gs_create_gdi_texture            gs_texture_create_gdi
gs_is_compressed_format          gs_is_compressed_format
gs_num_total_levels              gs_get_total_levels
texture_setimage                 gs_texture_set_image
cubetexture_setimage             gs_cubetexture_set_image
swapchain_destroy                gs_swapchain_destroy
texture_destroy                  gs_texture_destroy
texture_getwidth                 gs_texture_get_width
texture_getheight                gs_texture_get_height
texture_getcolorformat           gs_texture_get_color_format
texture_map                      gs_texture_map
texture_unmap                    gs_texture_unmap
texture_isrect                   gs_texture_is_rect
texture_getobj                   gs_texture_get_obj
cubetexture_destroy              gs_cubetexture_destroy
cubetexture_getsize              gs_cubetexture_get_size
cubetexture_getcolorformat       gs_cubetexture_get_color_format
volumetexture_destroy            gs_voltexture_destroy
volumetexture_getwidth           gs_voltexture_get_width
volumetexture_getheight          gs_voltexture_get_height
volumetexture_getdepth           gs_voltexture_getdepth
volumetexture_getcolorformat     gs_voltexture_get_color_format
stagesurface_destroy             gs_stagesurface_destroy
stagesurface_getwidth            gs_stagesurface_get_width
stagesurface_getheight           gs_stagesurface_get_height
stagesurface_getcolorformat      gs_stagesurface_get_color_format
stagesurface_map                 gs_stagesurface_map
stagesurface_unmap               gs_stagesurface_unmap
zstencil_destroy                 gs_zstencil_destroy
samplerstate_destroy             gs_samplerstate_destroy
vertexbuffer_destroy             gs_vertexbuffer_destroy
vertexbuffer_flush               gs_vertexbuffer_flush
vertexbuffer_getdata             gs_vertexbuffer_get_data
indexbuffer_destroy              gs_indexbuffer_destroy
indexbuffer_flush                gs_indexbuffer_flush
indexbuffer_getdata              gs_indexbuffer_get_data
indexbuffer_numindices           gs_indexbuffer_get_num_indices
indexbuffer_gettype              gs_indexbuffer_get_type
texture_rebind_iosurface         gs_texture_rebind_iosurface
texture_get_dc                   gs_texture_get_dc
texture_release_dc               gs_texture_release_dc