Bug 694025 - GLib drop support for adding interfaces after class_init

Without this Dia crashes at startup with new GLib version and the
DiaGdkRenderer being default. Make a new DiaGdkInteractiveRenderer which
follows the pattern also used for DiaCairoInteraciveRenderer. This should
be functional equivalent to what was there before and should work for all
current GLib versions.

(cherry picked from commit 213bdfe9)