mesa/teximage: accept ASTC formats for 3D texture specification

mesa/teximage: accept ASTC formats for 3D texture specification

The ASTC spec was revised as follows:

   Revision 2, April 28, 2015 - added CompressedTex{Sub,}Image3D to
   commands accepting ASTC format tokens in the New Tokens section [...].

Support only exists in the HDR submode:

   Add a second new column "3D Tex." which is empty for all non-ASTC
   formats. If only the LDR profile is supported by the implementation,
   this column is also empty for all ASTC formats. If both the LDR and HDR
   profiles are supported only, this column is checked for all ASTC
   formats.

LDR-only systems should generate an INVALID_OPERATION error when
attempting to call CompressedTexImage3D with the TEXTURE_3D target.

v2. return the proper error for LDR-only systems.
v3. update is_astc_format().
v4. use _mesa_is_astc_format().
v5. place logic in _mesa_target_can_be_compressed.
v6. fix issues handling ASTC formats.

Reviewed-by: Chad Versace <chad.versace@intel.com>
Signed-off-by: Nanley Chery <nanley.g.chery@intel.com>