Teach IOR about GPFS hints (gpfs_fcntl)

GPFS supports a "gpfs_fcntl" method for hinting various things,
including "i'm about to write this block of data".  Let's see if, for
the cost of a few system calls, we can wrangle the GPFS locking system
into allowing concurrent access with less overhead. (new IOR parameter
gpfsHintAccess)

Also, drop all locks on a file immediately after open/creation in the
shared file case, since we know all processes will touch unique regions
of the file.  It may or may not be a good idea to release all file locks
after opening.  Processes will then have to re-acquire locks already
held.   (new IOR parameter gpfsReleaseToken)