mesa/formatquery: Added texture gather/shadow related queries

mesa/formatquery: Added texture gather/shadow related queries

From the ARB_internalformat_query2 specification:

   "- TEXTURE_SHADOW: The support for using the resource with shadow samplers
      is written to <params>.

    - TEXTURE_GATHER: The support for using the resource with texture gather
      operations is written to <params>.

    - TEXTURE_GATHER_SHADOW: The support for using resource with texture gather
      operations with shadow samplers is written to <params>."

For all of them,

    "Possible values returned are FULL_SUPPORT, CAVEAT_SUPPORT, or NONE.
     If the resource or operation is not supported, NONE is returned."

Reviewed-by: Dave Airlie <airlied@redhat.com>