glsl: Add support for default layout qualifiers for uniforms.

glsl: Add support for default layout qualifiers for uniforms.

I ended up having to add rallocing of the ast_type_qualifier in order
to avoid pulling in ast.h for glsl_parser_extras.h, because I wanted
to track an ast_type_qualifier in the state.

Fixes piglit ARB_uniform_buffer_object/row-major.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>