Bug#988750: YAML dependencies should be optional/suggested

[dcook at prosentient.com.au]

Package: libcgi-session-serialize-yaml-perl
Version: 4.26-2

The Debian package requires that libyaml-perl or libyaml-syck-perl be
installed, but it is possible to use this package without either of those
YAML modules. You can specify your own YAML parser (like YAML::XS). 

There is some discussion about this on CPAN:
https://rt.cpan.org/Ticket/Display.html?id=136485
https://rt.cpan.org/Ticket/Display.html?id=136486

Tina Muller, an engineer at SUSE and the maintainer of
CGI::Session::Serialize::yaml, YAML, and YAML::XS, has also pointed out that
openSUSE doesn't require these dependencies:
https://build.opensuse.org/package/view_file/devel:languages:perl/perl-CGI-S
ession-Serialize-yaml/perl-CGI-Session-Serialize-yaml.spec?expand=1.