For 24 and 32 bit depth pictures xserver uses PICT_x8r8g8b8 and PICT_a8r8g8b8 formats,
which must be backed with GL_BGRA format. It is present in OpenGL ES 2.0 only with
GL_EXT_texture_format_BGRA8888 extension. We require such extension in glamor_init,
so, why not to make use of it?
Fixes #1208
Fixes #1354

Signed-off-by: Konstantin Pugin <ria.freelander@gmail.com>

Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Emma Anholt <emma@anholt.net>