Vala: Heap-buffer overflow in vala-gstreamer bindings at Gst.MapInfo()

The Gst.MapInfo function in Vala 0.26.0 and 0.26.1 uses an incorrect buffer length declaration for the Gstreamer bindings, which allows context-dependent attackers to cause a denial of service (crash) or possibly execute arbitrary code via unspecified vectors, which trigger a heap-based buffer overflow.