cogl-context-winsys: Avoid zero-length arrays
cogl-context-winsys: Avoid zero-length arrays

When compiling for non-glx platforms the winsys feature data array
ends up empty. Empty arrays cause problems for MSVC so this patch adds
a stub entry so that the array always has at least one entry.

Based on a patch by Ole André Vadla Ravnås

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