More static dispatch function removal.

More static dispatch function removal.

Make functions for the following extensions available only via
glXGetProcAddress.  In cases where there are other aliases to the same
functions (e.g., between GL_EXT_histogram and GL_ARB_imaging), the alias
functions may still be statically exported.

    - GL_ATI_blend_equation_separate
    - GL_EXT_blend_equation_separate
    - GL_EXT_convolution
    - GL_EXT_color_sub_table
    - GL_EXT_cull_vertex
    - GL_EXT_depth_bounds_test
    - GL_EXT_framebuffer_blit
    - GL_EXT_histogram
    - GL_EXT_multisample
    - GL_EXT_stencil_two_side
    - GL_EXT_timer_query
    - GL_IBM_multimode_draw_arrays
    - GL_INGR_blend_func_separate
    - GL_NV_fence
    - GL_SGI_color_table
    - GL_SGIS_multisample
    - GL_SGIS_pixel_texture
    - GL_SGIS_point_parameters
    - GL_SGIX_pixel_texture