mq: strip extra whitespace from node ids in header (issue2790) This makes `hg qpush --exact` work with patches created by `hg export`.

check-code: disallow calling opener(...).read() and opener(..).write()

prevent transient leaks of file handle by using new helper functions These leaks may occur in environments that don't employ a reference counting GC, i.e. PyPy. This implies: - changing opener(...).read() calls to opener.read(...) - changing opener(...).write() calls to opener.write(...) - changing open(...).read(...) to util.readfile(...) - changing open(...).write(...) to util.writefile(...)