p5-Imager support for gif

[Lars Balker Rasmussen]

Is there any reason not to have graphics/p5-Imager depend on libungif?
The package won't include support for gif unless either of the gif
libraries is present at installation time, so there's no gif support
if an organisation builds its own packages in a clean environment.

I propose adding 
	ungif:${PORTSDIR}/graphics/libungif
to LIB_DEPENDS

(and I depend on Imager for a project, so just give me maintainership)
-- 
Lars Balker Rasmussen                                        Consult::Perl