glsl: Account for location field when comparing interface blocks.

glsl: Account for location field when comparing interface blocks.

In commit e2660770731b018411fbe1620cacddaf8dff5287 (glsl: Keep track
of location for interface block fields), I neglected to update
glsl_type::record_key_compare to account for the fact that interface
types now contain location information.  As a result, interface types
that differ only by their location information would not be properly
distinguished.

At the moment this is not a problem, because the only interface block
in which location information != -1 is gl_PerVertex, and gl_PerVertex
is always created in the same way.  However, in the patches that
follow, we'll be adding new ways to create gl_PerVertex (by
redeclaring it), so we'll need location information to be handled
properly.

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