glsl: add ARB_ES3_1_compatibility support

Oddly a bunch of the features it adds are actually from ESSL 3.20. But
the spec is quite clear, oh well.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/compiler/glsl/glsl_parser_extras.h

@@ -510,6 +510,8 @@ struct _mesa_glsl_parse_state {
    /*@{*/
    /* ARB extensions go here, sorted alphabetically.
     */
+   bool ARB_ES3_1_compatibility_enable;
+   bool ARB_ES3_1_compatibility_warn;
    bool ARB_arrays_of_arrays_enable;
    bool ARB_arrays_of_arrays_warn;
    bool ARB_compute_shader_enable;