[libfko] Candidate build fix for Mac OS X 10.9 (closes #108)

Nikolay Kolev reported a build issue on Mac OS X 10.9 (Mavericks) where fwknop
copies of strlcpy() and strlcat() functions were conflicting with those that ship
with OS X 10.9.

The solution was to add a configure.ac check for strlcat() and strlcpy() and
wrap "#if !HAVE_..." checks around those functions.

A portion of the build errors looked like this:

/Applications/Xcode.app/Contents/Developer/usr/bin/make  all-recursive
Making all in lib
/bin/sh ../libtool  --tag=CC   --mode=compile gcc -DHAVE_CONFIG_H -I. -I..   -I ../common   -g -O2 -Wall -Wformat -Wformat-security -fstack-protector-all -fstack-protector -fPIE -D_FORTIFY_SOURCE=2 -MT base64.lo -MD -MP -MF .deps/base64.Tpo -c -o base64.lo base64.c
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I.. -I ../common -g -O2 -Wall -Wformat -Wformat-security -fstack-protector-all -fstack-protector -D_FORTIFY_SOURCE=2 -MT base64.lo -MD -MP -MF .deps/base64.Tpo -c base64.c  -fno-common -DPIC -o .libs/base64.o
In file included from base64.c:34:
In file included from ./fko_common.h:149:
./fko_util.h:56:9: error: expected parameter declarator
size_t  strlcat(char *dst, const char *src, size_t siz);
        ^
/usr/include/secure/_string.h:111:44: note: expanded from macro 'strlcat'
  __builtin___strlcat_chk (dest, src, len, __darwin_obsz (dest))
                                           ^
/usr/include/secure/_common.h:39:62: note: expanded from macro '__darwin_obsz'
 #define __darwin_obsz(object) __builtin_object_size (object, _USE_FORTIFY_LEVEL > 1 ? 1 : 0)
                                                             ^
[server] ignore pcap direction for sniffing link type DLT_NULL interfaces (fixes OS X 10.9 test suite runs)
[test suite] added DYLD_LIBRARY_PATH for Mac OS X 10.9
added extras/apparmor configure_args.sh helper script for building fwknop with args that AppArmor expects
minor extras/apparmor configure_args.sh path typo fix
[test suite] added support for 'otool' instead of 'ldd' on Mac OS X systems
[test suite] minor cleanup to remove uncessary 'fatal' test hash keys
[test suite] added Rijndael/HMAC compatibility tests for Mac OS X 10.9
[test suite] handle LD_LIBRARY_PATH from the main test-fwknop.pl script
[libfko] minor update to print 'None' for the HMAC type when an HMAC is not used instead of just diplaying '()'
minor hex_dump() formatting bug fix to properly align ascii remainder output
Merge branch 'mac_os_x_mavericks_build' of ssh://10.211.55.3/home/parallels/git/fwknop into mac_os_x_mavericks_build
[libfko] move is_base64 check to libfko

This commit replaces the separately implemented client/server
is_base64() check with a single libfko function, and libfko itself now
uses it as well before prepending Rijndael or GnuPG base64 encoded
prefixes.
[test suite] minor addition to fko-wrapper to call fko_errstr() across valid and invalid values
[test suite] added tests/code_structure.pl with a test for expected lib/fko.h error code fko_errstr() handling
[libfko] bug fix caught by new code structure error str test to add string for FKO_ERROR_INVALID_DATA_DECODE_EXTRA_TOOBIG