Import Gtk+ library

The library (and dependencies) was generated by gir-dylan, some manual changes
were made:

- Changed gobject-glue to use gobject and glib, removing duplicate functions
  and objects
- Fixed pkg-config library name for some libraries
- Changed the value of $MININT32 in glib-dylan to fix a crash while compiling

---

I tried compiling `duim-gtk` after this change, there are some serious warnings (most of them caused by missing functions and objects in Gdk) but it reaches the linking stage. At that point it seems to ignore the .jam files and it doesn't link the required libraries.