Don't need to save sys.stdin and sys.stdout anymore

Use local generated env instead of os.environ

Fix hg serve...

Fix TypeError

Change use of global sys.stdout, sys.stdin os.environ to a hgrequest object. Note: also change hgrequest.write(str(thing)) to hgrequest.write(thing), people should make sure they write strings.

Regenerate tcsh_completion after bugfix in generator script

tcsh_completion_build.sh: fixed error caused by xargs on Linux