The GTK2 and GTK3 backends for hiro implement a source-code editing widget
based on gtksourceview. gtksourceview2 in particular is quite old and
unmaintained, and Linux distros are keen to drop it, so removing the dependency
helps keep bsnes portable to future platforms -- especially since bsnes doesn't
*use* the source-editing widget anywhere. It's only used by Near's text-editor,
amethyst.
We could just rip out the gtksourceview-related code and be done with it,
but since Near is still around and still working on his own copy of hiro, I
asked him to contribute his implementation so that it will be easier to merge
any future changes too.
This adds two new hiro targets, "gtk2-se" and "gtk3-se" which include the
source-code editing widget and the gtksourceview dependency. Since bsnes
defaults to "gtk2" (without the dependency) we no longer need that package
installed to build bsnes.
Fixes#137.
