Bug 1074034, part 1: Remove vestiges of comm-central moz.build traversal, r=Standard8.
Bug 1074034, part 2: Replace $(MOZDEPTH) with $(DEPTH), r=Standard8
Bug 1074034, part 3: Use mozilla-central's baseconfig.mk instead of forking it, r=Standard8. a=jcranmer

A small complication arises in that we need to maintain distinct topsrcdir
variables, so we can't just delete this file. But we can make it as small as
possible.

Note that we don't include the mozilla-central version if INCLUDED_AUTOCONF_MK
is not defined, since topsrcdir (and hence MOZILLA_SRCDIR) is undefined.

Pushing to a CLOSED TREE because this is important to get to developers, since
it makes incremental builds work again!

--HG--
extra : amend_source : 5b4bca492ace69b5df399f49bf7aee5203b29adc