sshpeer: make remotelock a context manager

lock: turn a lock into a Python context manager This lets us greatly simply acquire/release cycles. Code pattern before: try: lock = repo.lock() # zillions of lines of code finally: lock.release() And after: with repo.lock(): # ...

with: use context manager for I/O in changedfiles in patch

with: use context manager for file I/O in memusage

i18n: don't translate a transaction name

chgserver: mark as a built-in extension

chgserver: import background server extension from cHg This extension is copied from https://bitbucket.org/yuja/chg/ -r 86feb5f2e971 It could be imported as mercurial/chgserver.py, but in that case, we would have to resolve circular import between chgserver and commandserver. So I decided to keep it as an extension. chgserver.chgcmdserver -> commandserver.server commandserver._servicemap -> chgserver.chgunixservice

check-code: export needs a space to avoid false positives