gtk.ffi: Find the right gtk library in a startup-hook. Necessary because gtk is not in the same place on varius distros, so just find it on demand. Fixes #1185.

basis/gtk/ffi/ffi.factor

@@ -2,8 +2,8 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: alien alien.c-types alien.destructors alien.libraries
 alien.libraries.finder alien.syntax assocs gobject-introspection
-gobject-introspection.standard-types kernel pango.ffi system
-vocabs ;
+gobject-introspection.standard-types init kernel pango.ffi
+system vocabs ;
 IN: gtk.ffi
 
 <<
@@ -14,10 +14,12 @@ IN: gtk.ffi
 LIBRARY: gtk
 
 <<
-"gtk" {
+[
+    "gtk" {
         { linux "gtk-x11-2.0" }
         { windows "libgtk-win32-2.0-0" }
-} os of [ find-library cdecl add-library ] [ drop ] if*
+    } os of [ find-library cdecl add-library ] [ drop ] if*
+] "find-gtk" add-startup-hook
 >>
 
 IMPLEMENT-STRUCTS: GtkTreeIter ;