that Valgrind will not complain about freed data structures that are
reachable via pointers.  This addresses Bug #45992 and Bug #46656.

This patch is mostly based on changes copied from branches/embedded-1.0,
mainly c5432, c3439, c3134, c2994, c2978, but also some other code was
copied.  Some added cleanup code is specific to MySQL/InnoDB.

rb://199 approved by Sunny Bains