diffstat: print 0 instead of nothing for 0 adds or removes
This is in line with how the stock diffstat behaves when processing a
single diff with no line modifications (like a binary diff).
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://mercurial.selenic.com/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.