Add port varient as irssi plugin

[arthur@…]

silc-client can be complied as a plugin for irssi. To enable this I altered the port file to add to the configure options:

                        --disable-asm \
+                        --with-silc-plugin=${prefix}/lib/irssi \
+                        --without-silc-includes

Ideally this would be a varient and have a dependancy on irssi.

I then needed to bodge the files in /opt/local/lib/irssi/modules to make the module loading work

 sudo ln -s libsilc_core.dylib libsilc_core.so
 sudo ln -s libfe_common_silc.dylib libfe_common_slic.so

I'm sure all of this could be done better, but the functionality is very useful.

[blb@…]

Hmm, so irssi won't load them unless they are named with .so? On the Mac either dylibs or so's can be dlopen()ed so obviously the symlink will work, but maybe we could update irssi to open either file type?