Make HgPoller break file paths correctly

The command to get revision info lists all files on one line and was
splitting on spaces to get file paths. Sometimes paths have spaces so
that doesn't work. Instead, insert a pathsep character between paths
and use that for splitting.

This fixes http://trac.buildbot.net/ticket/2595
Merge branch 'master' of git://github.com/shoelzer/buildbot