Find Tivoli TSM headers in 64 bit location

Find Tivoli TSM headers in 64 bit location

When building with --enable-tivoli-tsm locate the Tivoli TSM headers
if they are installed in the path used by the 64 bit Tivoli TSM
installation.

Change-Id: I4f114a4ada1babcbe1e52f451f10e78d861b7fd0
Reviewed-on: https://gerrit.openafs.org/12258
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>