convert xstat and friends to pthreads

convert xstat and friends to pthreads

Convert the xstat, fsprobe, and gtx libraries and test programs to
pthreads. Build these libraries with libtool.

Build the scout and afsmonitor programs with pthreads instead of LWP.

Change-Id: Ie1737e71b4e57735bf7b6c7dc3177d717ea35ac6
Reviewed-on: https://gerrit.openafs.org/12753
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>