glossary: fixed typo in "Directory, working" description
The term "Directory, working" referenced a non-existant term named "Parents,
working directory". This patch fixes the typo.
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.