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
Merge pull request #513 from fracek/duim-gtk

Import Gtk+ library