Correct si_code for the SIGBUS signal generated by the alignment trap.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Correct the problem reported by test16 from
tools/regression/file/flock/flock.c, which completes the fix in
r192685.  When the lock was stolen from us, retry the whole lock
sequence in kernel, instead of returning EINTR to usermode and hoping
that application would handle it correctly by restarting the lock
acquire.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Make this compilable on latest Linux'es without warnings.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week