A first SDL 2.0 GL renderer implementation
covers in BlitGameSprite
Add transparency support for masks
Memory usage optimization (no any textures created before needed). 32bpp sprites now support color keys.
Some bugfixes
GLVideoDriver: few bugfixes (thanks fuzzie). Add an error handling during shader programs creation.
GLVideoDriver: Implemented GLPaletteManager class to share palette textures between sprites (greatly reduces memory usage)
glPaletteTexture = 0 in copy constructor
GLVideoDriver: Add another RemovePaletteTexture method (by texture id), some code polishing
GLVideoDriver: Some fixes (Covering, attached palettes)
GLVideoDriver: More clean, more stable. Fixed problems with attached palettes. Implemented GetScreenshot()
GLVideoDriver: Some fixes.
GLVideoDriver: MakeUnused() destroys all textures
GLVideoDriver: Removed attachedPalette from GLSprite. Added acqure & release to paletteManager for all palettes, added support to attached palettes (separate map), cleanup every frame.
GLVideoDriver: Fixed leaks with palettes (thanks fuzzie). Fixed tint in BlitGameSprite.
GLVideoDriver: GLSLProgram class to manage programs, Shader class removed, changes in shaders, DrawEllipse
GLVideoRenderer: Shader source files. GLSLProgram now load shaders from text files. Automatically storing uniform locations during program creation.
GLVideoDriver: Fixed DrawHLine & DrawVLine, implemented DrawCircle (with DrawEllipse)
GLVideoDriver: some fixes
GLVideoDriver: Another method to drawing lines, implementing DrawLine, removed 'transpose' param from GLSLProgram::SetUniformMatrixValue

 (always GL_FALSE in GLES)