chgserver: add utilities to calculate confighash
confighash is the hash of sensitive config items like [extensions], and
sensitive environment variables like HG*, LD_*, etc. The config items
can come from global, user, repo config, and command line flags.
For chgserver, it is designed that once confighash changes, the server is
not qualified to serve its client and should redirect the client to a new
server. The server does not need to exit in this case, since it can still
be valid (have a matched confighash) to serve other chg clients.
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
http://docutils.sourceforge.net/
Use the Makefile in this directory to generate the man and HTML pages.