mq: record more data in patchheader class (no behavior changes) * parse branch and nodeid header lines * remember the line number where diffs started Combined, these make mq.patchheader() very useful for parsing and preserving a patch header through edits. TortoiseHg will use the nodeid and parent to display these header datums in the graph when patches are unapplied, and uses diffstartline to parse patch files using record.parsepatch().