Revert files with no local changes to their vendor state to ease future
upgrading.
 - Convert the bufobj lock to rwlock.
 - Use a shared bufobj lock in getblk() and inmem().
 - Convert softdep's lk to rwlock to match the bufobj lock.
 - Move INFREECNT to b_flags and protect it with the buf lock.
 - Remove unnecessary locking around bremfree() and BKGRDINPROG.

Sponsored by:	EMC / Isilon Storage Division
Discussed with:	mckusick, kib, mdf