K 10
svn:author
V 3
phk
K 8
svn:date
V 27
2004-08-19T19:51:51.000000Z
K 7
svn:log
V 343
Add bioq_takefirst().

If the bioq is empty, NULL is returned.  Otherwise the front element
is removed and returned.

This can simplify locking in many drivers from:

	lock()
	bp = bioq_first(bq);
	if (bp == NULL) {
		unlock()
		return
	}
	bioq_remove(bp, bq)
	unlock
to:
	lock()
	bp = bioq_takefirst(bq);
	unlock()
	if (bp == NULL)
		return;

END