[client] minor man page wording update for backwards compatibility section
[test suite] added backwards compatibility tests with a dual usage key in access.conf
[test suite] additional --save-rc-stanza tests for vars not printed in fwknop client decode output
added missing test suite conf/ files to Makefile.am
[libfko] use local strndup() if autoconf HAVE_STRNDUP not defined

Blair Zajac reported that strndup() is not available on some PPC systems, so
this commit switches to use the local lib/fko_util.c implementation similarly
to what is done for Windows systems.
[libfko] handle endian detection on PPC (and other) systems

Blair Zajac contributed a patch to handle endian detection on PPC systems
and issue a compile time error if it cannot be determined.  This commit affects
the BYTEORDER macro.
bump version to 2.5-pre2
[test suite] minor bug fix to add 'iptables' to custom chain test titles