serve: fix https mode and add test
The https mode failed in super because BaseRequestHandler is an old-style
class.
This introduces the first test of https client/server functionality - and
"hghave ssl". The test is currently only run on Python 2.6.
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.