mesa: new _mesa_error_check_format_and_type() function

mesa: new _mesa_error_check_format_and_type() function

This replaces the _mesa_is_legal_format_and_type() function.

According to the spec, some invalid format/type combinations to
glDrawPixels, ReadPixels and glTexImage should generate
GL_INVALID_ENUM but others should generate GL_INVALID_OPERATION.

With the old function we didn't make that distinction and generated
GL_INVALID_ENUM errors instead of GL_INVALID_OPERATION.  The new
function returns one of those errors or GL_NO_ERROR.

This will also let us remove some redundant format/type checks in
follow-on commit.

v2: add more checks for ARB_texture_rgb10_a2ui at the top of
_mesa_error_check_format_and_type() per Ian.

Signed-off-by: Brian Paul <brianp@vmware.com>