[tests] Some improvements for test-pixmap
[tests] Some improvements for test-pixmap

The test no longer requires an XID argument to run; instead it creates its
own X Window. The test now also aims to demonstrate whether mipmapping is
working, and clearly informs you if fallbacks are being used for GLX tfp.

djdeath/clutter-android,jigpu/clutter,rkudiyarov/clutter_osx,collects/clutter,jigpu/clutter,djdeath/clutter-multithreaded,Distrotech/clutter,spatulasnout/clutter,rkudiyarov/clutter_osx,kerrickstaley/clutter-vala,collects/clutter,tardyp/clutter,rkudiyarov/clutter_osx,djdeath/clutter-multithreaded,rkudiyarov/clutter_osx,collects/clutter,nobled/clutter,heysion/clutter-clone,djdeath/clutter-multithreaded,djdeath/clutter,jigpu/clutter,collects/clutter,djdeath/clutter-android,heysion/clutter-clone,nobled/clutter,GNOME/clutter,jigpu/clutter,ebassi/clutter,ebassi/clutter,dlespiau/clutter,kerrickstaley/clutter-vala,ebassi/clutter,spatulasnout/clutter,jigpu/clutter,Distrotech/clutter,GNOME/clutter,spatulasnout/clutter,djdeath/clutter,nobled/clutter,djdeath/clutter,collects/clutter,GNOME/clutter,kerrickstaley/clutter-vala,tardyp/clutter,djdeath/clutter,djdeath/clutter-android,Distrotech/clutter,spatulasnout/clutter,jigpu/clutter,GNOME/clutter,kerrickstaley/clutter-vala,djdeath/clutter-android,ebassi/clutter,djdeath/clutter-android,djdeath/clutter-multithreaded,Distrotech/clutter,dlespiau/clutter,ebassi/clutter,dlespiau/clutter,heysion/clutter-clone,heysion/clutter-clone,Distrotech/clutter,Distrotech/clutter,GNOME/clutter,djdeath/clutter,tardyp/clutter,heysion/clutter-clone,djdeath/clutter,spatulasnout/clutter