gst1-libav: bump version

Bug reports fixed in this release:

      * 727779 : avdec_h264, matroskademux: crash while seeking (1.2 regression)

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gstreamer1/gst1-libav/gst1-libav.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-GST1_LIBAV_VERSION = 1.2.3
+GST1_LIBAV_VERSION = 1.2.4
 GST1_LIBAV_SOURCE = gst-libav-$(GST1_LIBAV_VERSION).tar.xz
 GST1_LIBAV_SITE = http://gstreamer.freedesktop.org/src/gst-libav