See README for instructions.

net: added raw_cb.c, raw_cb.h, raw_usrreq.c, unmodified. control block implementation for raw sockets

Some mutex work.

prex code depends on this.

TODO: make it optional

It just adds complexity, and doesn't reduce locking overhead, as we must
take the spinlock anyway during unlock.

Remove it, since it makes conversion to a recursive mutex (needed
by fs/vfs/vfs_mount.c) more complicated.

* 'master' of github.com:cloudius-systems/osv:
  gdb: pretty printers for libstdc++
  sched: start the reaper thread
  printf: reduce stack usage