This switches plan9/u9fs to another upstream which has seen some small
development over the time, following what other package repositories
already did: https://bitbucket.org/plan9-from-bell-labs/u9fs
port-wise:
- tweak the COMMENT
- drop unneeded patches
- install u9fs in sbin/ rather than bin/
- install the manpage (and tweak it so it's useful in here.)
maintainer timeout, ok sthen@
e99aee537c