Update pseudo to 1.5.1

Update pseudo to 1.5.1

pseudo 1.5's enable-force-async works great, unless you use a host
where, inexplicably, stat(2) reports inconsistent and changing values
for a file's size or times for some time unless a file has been fsynced,
in which case you might want a way to cause an fsync to work.

Also noticed that some recent changes never made it into the docs, so
I did a little cleanup there. And changed the way NDEBUG suppresses
pseudo's debug messages, so arguments to them with possible side
effects (like calls into functions in another translation unit) can be
omitted, which should drastically reduce computational time if anyone
ever uses NDEBUG.

(From OE-Core rev: 150174d52adefdefe62e2ed0598665481591e4c2)

Signed-off-by: Peter Seebach <peter.seebach@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>