prdb_check: fix out of bounds array access in continuation entries

prdb_check: fix out of bounds array access in continuation entries

A continuation entry (struct contentry) contains 39 id elements, however
a regular entry (struct prentry) contains only 10 id elements.
Attempting to access more than 10 elements of a regular entry is
undefined behavior.

Use a stuct contentry when when processing continuation entries in
prdb_check.  This is done to safely traverse the id arrays of the
continuation entries.  Use the new pr_PrintContEntry to print
continuation entries.

The undefined behavior manfests as a segmentation violation in
WalkNextChain() when built with GCC 4.8 with optimization enabled.

Reviewed-on: http://gerrit.openafs.org/11742
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 15e8678661ec49f5eac3954defad84c06b3e0164)

Change-Id: Ifc0682cd2b6b1590b10c44ccdda181fd4227c1c2
Reviewed-on: http://gerrit.openafs.org/12104
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>