Add built-in debug malloc wrapper.

Add built-in debug malloc wrapper.

TODO: Remove the completed TODO item.

configure.in: Add --with-malloc=srvx support.

src/Makefile.am: Add alloc-srvx.c to extra sources.

src/common.h: Reindent debug malloc directives; add directives for
WITH_MALLOC_SRVX.

src/dict-splay.c: Kludge around free() as macro vs function.
git-archimport-id: srvx@srvx.net--2005-srvx/srvx--devo--1.3--patch-4