i965/blorp: Make brw_blorp_params::get_wm_prog() a C-style virtual function.

Future patches in this series will require calling
brw_blorp_params::get_wm_prog() from C code.  So change it to a
C-style virtual function (with the function pointer explicit in the
struct).
i965/blorp: Convert brw_blorp_mip_info into a C struct
i965/blorp: Convert brw_blorp_surface_info into a C struct
i965/blorp: Convert brw_blorp_coord_transform_params into a C struct
i965/blorp: Convert brw_blorp_wm_push_constants into a C struct
i965/blorp: Convert more stuff to C
Convert more stuff to C
Convert the rest of brw_blorp.h to C
!UPSTREAM: i965/blorp: Merge into brw_wm_prog.

TODO: disentangle prep work.
i965/blorp: Use gen7_push_constant_alloc
i965/blorp: Use the same binding table assignments as normal rendering.

This should make it easier to merge blorp code with the state atoms
for normal rendering.
i965/blorp: Merge into gen6_multisample_state.
i965/blorp: Use brw_state_base_address.
i965/blorp: Merge into brw_vertices.
i965/blorp: Merge into gen{6,7}_urb.
i965/blorp: Merge into gen6_blend_state.
i965/blorp: Merge into gen6_color_calc_state.
i965/blorp: Use gen7_blend_state_pointer.
i965/blorp: Use gen7_cc_state_pointer.
i965/blorp: Merge into gen6_depth_stencil_state.