GLib RFC: Improve checking provided with --enable-mem-check

[Richard Braakman]

I wrote something similar for the Kannel project (http://www.kannel.org,
file gwlib/gwmem-check.c).  You might want to look at it for ideas.
It's fast enough to be used as the default memory manager for Kannel.

It doesn't have "overflow" lists, though -- it figures that if Kannel
allocates too many blocks, there's bound to be a memory leak :)  That
model probably doesn't apply to an application like GnuCash, which
needs to keep a large amount of data in memory.

Richard Braakman