pointers are not castable to unsigned int

When printing a pointer's value for debugging purposes, use the
dedicated printf format specifier for pointers instead of assuming
that unsigned int ('x') is good enough.

Found by clang on FreeBSD 10.0.

Reviewed-on: http://gerrit.openafs.org/10820
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 758ec15f9391c296f1caa042385148f1a5e0bc84)

Change-Id: Ibe88c38d0563ac125486d0ae7f16882a7989ee98
Reviewed-on: http://gerrit.openafs.org/11402
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>