* autoload.cc (CancelSynchronousIo): Define.
	* fcntl.cc (fcntl64): Drop handling of locking commands.
	* fhandler.h (class fhandler_disk_file): Add mandatory_locking.
	(fhandler_disk_file::fcntl): Declare.
	(fhandler_disk_file::mand_lock): Declare.
	* fhandler_disk_file.cc (fhandler_disk_file::fhandler_disk_file):
	Initialize mandatory_locking.
	(fhandler_disk_file::fcntl): New method.  Handle F_LCK_MANDATORY and
	locking commands.
	(fhandler_disk_file::dup): Duplicate mandatory_locking.  Fix a bug
	when duplicating prw_handle failed.
	(fhandler_disk_file::fixup_after_fork): Reset mandatory_locking.
	* flock.cc (fhandler_disk_file::lock): Add comment.
	(struct lock_parms): New struct to pass parameters to blocking_lock_thr
	thread function.
	(blocking_lock_thr): New thread function.
	(fhandler_disk_file::mand_lock): New methof implementing mandatory
	locking with Windows semantics.
	* ntdll.h (NtLockFile): Declare.
	(NtUnlockFile): Declare.
	* include/fcntl.h: Fix a comment.
	(F_LCK_MANDATORY): Define.  Add lengthy comment to explain.
	* new-features.xml (ov-new1.7.19): Add mandatory locking.
Fix typo