[plt-dev] update on experiment in re-implementing MrEd

[Jon Rafkind]

>       * Unix/X11: Install GtK and Cairo. (You almost certainly have
>         them already.)
>
>   
On my system I have /usr/lib/libcairo.so.2, not libcairo.2.so, so 
loading (ffi-lib "libcairo.2") fails.