mesa: Fix the core GL genned-name handling for glBindBufferBase()/Range().

mesa: Fix the core GL genned-name handling for glBindBufferBase()/Range().

This is part of fixing gl-3.1/genned-names.

v2: Fix a missing return value.

NOTE: This is a candidate for the 9.0 branch.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>