TESTS to check consistency between O_DIRECT reads/writes and buffered
reads/writes and truncate.

PROGRAMS:

dio_append - append to zeroed data to a file using O_DIRECT while a
		child process is doing buffered reads and check
		if the child always sees zero.

dio_sparse - write zeroed data to a sparse area in file using O_DIRECT
		while a child process is doing buffered reads and
		check if the child always sees zero.

dio_truncate - write zeroed data to a file using O_DIRECT, then
		truncate the file, write NON-ZERO data to a 2nd
		file and truncate the 2nd file, while a child process
		is constantly reading the 1st file O_DIRECT and
		checking for zero data.

aiodio_append - like dio_append, but uses AIO.

aiodio_sparse - like dio_sparse, but uses AIO

direct_read_under.c - test Stephen Tweedie wrote to expose the DIO
		 races (the testcase issues buffered writes and dio reads).