mq: backup local changes in qpop --force (issue3433)

pager: remove quiet flag With the pager running as a child process, exiting the pager doesn't result in a broken pipe message. To distinguish the exit broken pipe code from a mercurial abort we register the default action for SIGPIPE. This results in a 141 exit code instead of a 255. On windows SIGPIPE doesn't exists and a ValueError will be thrown.