Add package: luakit

This patch adds the luakit browser. It has to be build using lua5.1, I
tried 5.2 but I couldn't run luakit due to a runtime error with it.

It also uses gtk3 here, override to use gtk2, which should also work.

Suggested-by: Benno Fünfstück <benno.fuenfstueck@gmail.com>