Bug 968259 - Update mach mercurial-setup to work with new unified VCS tools repo; r=ted

bzexport is now pulled from its new canonical home. The old location can
be cleaned if the user agrees to it. The new location is updated in the
hgrc.

DONTBUILD (NPOTB)

--HG--
extra : rebase_source : f7737bcf7b528df9b8130ecb3cf73f4d74280d3b
extra : amend_source : b9a1a0b656b1e350cf161db386cf7986cac6a430