mesa: add a GLES3.2 enums section, and expose new MS line width params

mesa: add a GLES3.2 enums section, and expose new MS line width params

This also exposes them for ARB_ES3_2_compatibility.

While both specs refer to the new MS line width parameters being
separate from the existing AA line widths, reality begs to differ. It's
the same on all hardware currently supported by mesa. Should hardware
come along that wants these to be different, they're easy enough to
separate out.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> (v1)
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>