Make looks for gtk2-gir with gtk3

[John Frankish]

compiling midori-0.5.11 with -DUSE_GTK3=ON -DUSE_GIR=ON, make fails looking for gtk2 gir files:

make[2]: Entering directory '/usr/src/midori-0.5.11/build'
cd /usr/src/midori-0.5.11/build/gir && /usr/local/bin/g-ir-scanner -Imidori -I/usr/src/midori-0.5.11/ -I/usr/src/midori-0.5.11/build/midori -I/usr/src/midori-0.5.11/katze -I/usr/src/midori-0.5.11/toolbars -I. --header-only -n Katze --identifier-prefix Katze /usr/src/midori-0.5.11/katze/katze-*.c /usr/src/midori-0.5.11/katze/katze-*.h --pkg gtk+-2.0 --pkg webkit-1.0 --pkg gio-2.0 --pkg gobject-2.0 --warn-all -iGObject-2.0 -iGLib-2.0 -iGtk-2.0 --nsversion 0.5 -o /usr/src/midori-0.5.11/build/gir/Katze-0.5.gir
Couldn't find include 'Gtk-2.0.gir' (search path: '[u'gir-1.0', u'/usr/local/share/gir-1.0', u'/usr/share/gir-1.0', u'/usr/local/share/gir-1.0']')
make[2]: *** [gir/CMakeFiles/g-ir-scanner_katze.dir/build.make:60: gir/CMakeFiles/g-ir-scanner_katze] Error 1
make[2]: Leaving directory '/usr/src/midori-0.5.11/build'
make[1]: *** [CMakeFiles/Makefile2:7446: gir/CMakeFiles/g-ir-scanner_katze.dir/all] Error 2
make[1]: Leaving directory '/usr/src/midori-0.5.11/build'
make: *** [Makefile:144: all] Error 2