glsl: mark special built-in inputs referenced by vertex stage
glsl: mark special built-in inputs referenced by vertex stage

Refactoring done on active attribute queries did not take in to
account special built-in inputs for the vertex stage. This commit
sets them referenced by vertex stage so that they get enumerated
properly.

Fixes Piglit test 'get-active-attrib-returns-all-inputs' failure.

Signed-off-by: Tapani Pälli <cdcb67a5e49297de94340ca09f25994bd5e7f762@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90243
Acked-by: Jose Fonseca <61b5a29db2c0650f7c8510f93eece059c1b09320@vmware.com>
Tested-by: Dieter Nützel <902ea9f4f1fbe947e8e8c77ca59f21dfca158b7e@nuetzel-hh.de>
Reviewed-By: Martin Peres <f078f77bcd6141e84e4eefdc58402db4e0e36622@linux.intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler