Avoid variable length arrays in clutter-backend-x11
Avoid variable length arrays in clutter-backend-x11

There was an array whose length was define by a static const int
variable. GCC seems to consider this a variable-length array so it
will cause warnings now that -Wvla is enabled. We might as well make
this constant a #define instead to avoid the warning.

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