Post-release version bump to 1.5.7
Post-release version bump to 1.5.7

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