[gles] Fix computation of camera distance
[gles] Fix computation of camera distance

Port the fix in commit f409b58e to the GLES implementation of
COGL.

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