- Add a new 'flags' parameter to getblk().

 - Add a new 'flags' parameter to getblk().
 - Define one flag GB_LOCK_NOWAIT that tells getblk() to pass the LK_NOWAIT
   flag to the initial BUF_LOCK().  This will eventually be used in cases
   were we want to use a buffer only if it is not currently in use.
 - Convert all consumers of the getblk() api to use this extra parameter.

Reviwed by:	arch
Not objected to by:	mckusick