cogl: don't include cogl-vector.h twice in cogl.h
cogl: don't include cogl-vector.h twice in cogl.h

cogl-vector.h should only be included by cogl.h when
COGL_ENABLE_EXPERIMENTAL_API is defined. This removes the unguarded
duplicate include.

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