Add tests/printenv.py
This is a small script that can be used as a hook to print the
HG_* environment variables without relying on the shell.
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.