Inline::Perl5 does not (yet) work with perl builds configured with -Duselongdouble

I was initially all set up to use a -Dusequadmath build of perl, but I've now scaled back my expectations a little and decided that might have been a bit "over the top" ;-)
I've therefore switched to perl 5, version 20, subversion 0 (v5.20.0) built for x86_64-linux-thread-multi.

Thanks for the heads-up on that aspect, Tux.

Cheers,
Rob