1068. [bug] errno could be overwritten by catgets(). [RT #1921]
1066. [bug] Provide a thread safe wrapper for strerror().
[RT #1689]
(Also some changes to configure.in, config.h.in, and acconfig.h that were
necessary to allow config.h.in to be correctly regenerated with the
HAVE_STRERROR definition needed by 1066.)