Windows support

Several fixes to support windows build.

1) C function  gtk_recent_info_get_applications accepts a pointer to 'gulong' as a second argument. Unsigned long is 64bit on linux but 32 bit on windows.
2) Now examples don't link - undefined references to gtk_glue cast_Gtk* symbols. It seems that functions in #ifdef GTK_ conditionals are not included, because GTK_VERSION define is not passed to the gcc.
3) More undefined references to gtk_glue. #ifdef GTK_* conditionals are wrong. 3_6 symbols exist in 3_10 and 3_12, 3_10 in 3_12. Uncommented GApp* stuff in gtk_glue.
4) Linking errors on g_app* symbols. Passing gio to link flags fixes this.
5) Linking examples produces 'undefined reference' errors to gtk_* symbols. Passing rgtk.rs to rustc before -L $(GLUE_DST) seems to fix this (rustc magic?).

Tested on windows using msys2_64, linux64. Gtk version 3.13. Rgtk built for GTK_3_12.