Fix tgz archival on Windows.
Making tgz's on Windows has been broken by 06de65673ec2
due to not being careful enough about binary mode opens.
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://www.selenic.com/mercurial/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.