Bug 6244

When some external perl modules fail on a 'require', the SpamAssassin
installation procedure reports 'optional module out of date',
instead of showing a failure reason. For example:

$ perl Makefile.PL
[...]
optional module out of date: IO::Socket::INET6
optional module out of date: IO::Socket::SSL
optional module out of date: Compress::Zlib


Trying to load these modules from a command line shows that they are the
latest version, but fail to compile for whatever reason, like an incompatible
(old) version of perl, or whatever. For example (with perl 5.6.2):

$ perl -e 'use IO::Socket::INET6; print IO::Socket::INET6->VERSION,"\n"'
Bareword "AF_INET6" not allowed while "strict subs" in use at /usr/local/lib/perl5/site_perl/5.6.2/IO/Socket/INET6.pm line 58.

$ perl -e 'use IO::Socket::SSL; print IO::Socket::SSL->VERSION,"\n"'
Constant name 'HASH(0x815f844)' has invalid characters at /usr/local/lib/perl5/site_perl/5.6.2/IO/Socket/SSL.pm line 25

$ perl -e 'use Compress::Zlib; print Compress::Zlib->VERSION,"\n"'
Can't locate Scalar/Util.pm in @INC (@INC contains: ...)
at /usr/local/lib/perl5/site_perl/5.6.2/Compress/Zlib.pm line 9.