Commit Briefs
fix clang warnings reported by Tuncer Ayaz
R=rsc http://codereview.appspot.com/6744054
delete 9P2000.u
thanks to Erik Quanstrom R=rsc http://codereview.appspot.com/3469042
Experiment: ignore double-responds.
Also allow nil string as empty string in readstr.
Small tweaks
Lots of new code imported.