Preliminary version of resize_ffs, based on der Mouse's fsresize tool.
I didn't have time to clean it up completely before my legal status
w.r.t. open source projects goes into limbo for a while.  Other
developers are encouraged to play with the tool and get it into
release-worthy shape.

TODO list (see TODO file)

* -current; put it into release lists/etc. and src/sbin/Makefile
  (built & tested on 1.6.1)
* make it ask questions before doing any work (confirm)
* create regression test suite (see discussions on tech-kern and
  developers) and fix any bugs
* verify conversion to ANSI C didn't break anything
* port to UFS2