cogl-atlas: Try the next size when there would be less than 6% waste
cogl-atlas: Try the next size when there would be less than 6% waste

Previously when the atlas needs to be migrated it would start by
trying with the same size as the existing atlas if there is enough
space for the new texture. However even if the atlas is completely
sorted there will always be some amount of waste so when the atlas
needs to grow it would usually end up redundantly trying the same size
when it is very unlikely to fit. This patch changes it so that there
must be at least 6% waste available after the new texture is added
otherwise it will start with the next atlas size.

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