tests: record few more daemon pids to be safe

tests: add timeouts, make run-tests.py clean up dead daemon processes test timeout feature is needed for test with python 2.5 beta. if test does not complete in time (30 seconds is default), it is killed. some times daemon process used in test can be alive after the test is killed by user or by timeout. tests now record daemon pids into $DAEMON_PIDS and run-tests.py kills all living daemons after every test. final little change is to add newline to end of pid file printed by "hg serve", else "cat hg.pid >> $DAEMON_FILES" gives garbage.

run-tests.py: make tests use same python interpreter as test harness. this is wanted because some tests run python interpreter directly. must use same python interpreter in tests as in main harness or problems will happen because of e.g. different python abi if run-tests.py run with python 2.5 but system python is 2.4. fix is to see if system python is used and is named python. if no, put symlink called python at front of shell search path.

HTTPS: fix python2.3, persistent connections, don't explode if SSL is not available The urllib2 differences between python 2.3 and 2.4 are hidden by using keepalive.py, which also gives us support for persistent connections. Support for HTTPS is enabled only if there's a HTTPSHandler class in urllib2. It's not possible to have separate classes as handlers for HTTP and HTTPS: to support persistent HTTPS connections, we need a class that inherits from both keepalive.HTTPHandler and urllib2.HTTPSHandler. If we try to pass (an instance of) this class and (an instance of) the httphandler class to urllib2.build_opener, this function ends up getting confused, since both classes are subclasses of the HTTPHandler default handler, and raises an exception.