tlsdate-helper: Include the CA cert container path in error messages

It makes debugging permission issues or incorrect paths more convenient.
return-argc: Fix prototype to silence compiler complaint
tlsdate-helper: Remove a pointless assignment
Fix a small memory leak in a conf_parse() error path
Fix a typo in the Mac OS X instructions
autogen.sh: Ignore autoconf warnings on FreeBSD

Prevents "upstream" issues like:

fk@r500 ~/git/tlsdate $./autogen.sh
autoreconf-2.69: Entering directory `.'
autoreconf-2.69: configure.ac: not using Gettext
autoreconf-2.69: running: aclocal --force -I m4
aclocal-1.12: warnings are treated as errors
/usr/local/share/aclocal/libxosd.m4:9: warning: underquoted definition of AM_PATH_LIBXOSD
/usr/local/share/aclocal/libxosd.m4:9:   run info Automake 'Extending aclocal'
/usr/local/share/aclocal/libxosd.m4:9:   or see http://www.gnu.org/software/automake/manual/automake.html#Extending-aclocal
autoreconf-2.69: aclocal failed with exit status: 1
Add FreeBSD support for tlsdate and tlsdate-helper
Merge conflict issues
Add FreeBSD support for tlsdate and tlsdate-helper
configure.ac: Add an explicit check for fmemopen on FreeBSD

The unit tests need it and segfault if the autoconf
goo picks up a compiler that hides the prototype.
Makefile.am: Only try to run tlsdated_unittest on GNU/Linux

It currently doesn't compile on FreeBSD (and probably Mac OS X).
Only tested on FreeBSD where this commit gets the "check" target working.
Install GNU/Linux-only files only on GNU/Linux

Only tested on FreeBSD.
Re-add CHANGELOG entry that conflicted with freebsd-port
elif not elseif to compile on GNU/Linux; did this work on FreeBSD?