Copy new cacheio functions used by svcgssd to nfslib

Copy private qword_ functions from the svcgssd version into
the general nfslib library.   Add prototypes as needed.
Also, update readline to use a bigger buffer allocation as is
needed in the svcgssd version.

Signed-off-by: Kevin Coffman <kwc@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>