mesa: update glext.h to version 20130624

mesa: update glext.h to version 20130624

In glapi_priv.h we always need the typedef for the GLclampx type
since GL_OES_fixed_point is now defined in glext.h but the
GLclampx type is not.  GLclampx is not used by anything in glext.h
but we need it for GL ES dispatch.

This is a huge patch because the structure of the file has been
changed.

The following extensions are new, however:

GL_AMD_interleaved_elements
GL_AMD_shader_trinary_minmax
GL_IBM_static_data
GL_INTEL_map_texture
GL_NV_compute_program5
GL_NV_deep_texture3D
GL_NV_draw_texture
GL_NV_shader_atomic_counters
GL_NV_shader_storage_buffer_object
GL_NVX_conditional_render
GL_OES_byte_coordinates
GL_OES_compressed_paletted_texture
GL_OES_fixed_point
GL_OES_query_matrix
GL_OES_single_precision

And these extensions were removed:

GL_FfdMaskSGIX
GL_INGR_palette_buffer
GL_INTEL_texture_scissor
GL_SGI_depth_pass_instrument
GL_SGIX_fog_scale
GL_SGIX_impact_pixel_texture
GL_SGIX_texture_select

Reviewed-by: José Fonseca <jfonseca@vmware.com>