glamor: Fix handling of 1-bit pixmaps

Since 8702c938 the pixmap formats are handled in a single place. In the process of conversion the difference between pixmap formats that can be uploaded and those that can be rendered on GL side has been lost. This affects only 1-bit pixmaps: as they aren't supported on GL, but can be converted to a R8 or A8 format for rendering (see glamor_get_tex_format_type_from_pictformat()).

To work around this we add a separate flag that specifies whether the format actually supports rendering in GL, convert all such checks to use this flag and then add 1-bit pixmap formats that don't support rendering in GL.

Fixes: 8702c938

Fixes: #1210 (closed)

cc: @ofourdan @anholt