cogl-rectangle-map: Record largest gap rather than the remaining space
cogl-rectangle-map: Record largest gap rather than the remaining space

Previously each node in the rectangle map tree would store the total
remaining space in all of its children to use as an optimization when
adding nodes. With this it could skip an entire branch of the tree if
it knew there could never be enough space for the new node in the
branch. This modifies that slightly to instead store the largest
single gap. This allows it to skip a branch earlier because often
there would be a lot of small gaps which would add up to enough a
space for the new rectangle, but the space can't be used unless it is
in a single node.

The rectangle map still needs to keep track of the total remaining
space for the whole map for the debugging output so this has been
added back in to the CoglRectangleMap struct. There is a separate
debugging function to verify this value.

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