bug - GCompareFunc used inconsistently

[Jeff Garzik <jgarzik pobox com>]

For some modules, GCompareFunc returns a value in the same manner as
strcmp, where equal values result in zero.  glist, gmem, gslist, and
gtree do this.

For other modules, GCompareFunc returns a truth value, where equal
values result in one.  gcache, ghash, and grel do this.

This has already resulted in one recent bug report, and will probably be
a source of confusion.

Would be the course of action be to define a GEqualFunc type which
returns a gboolean, and change ghash, gcache, and grel accordingly?

	Jeff