cogl-framebuffer: fix leak when popping framebuffer
cogl-framebuffer: fix leak when popping framebuffer

We were using g_slist_remove_link instead of g_slist_delete_link
resulting in a memory leak. Thanks to Simon Lanzmich for
reporting this bug.

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