gifdec.c was removed, purge its entry from the Makefile.

Originally committed as revision 14228 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/Makefile

@@ -53,7 +53,6 @@ OBJS-$(CONFIG_FLV_MUXER)                 += flvenc.o avc.o
 OBJS-$(CONFIG_FOURXM_DEMUXER)            += 4xm.o
 OBJS-$(CONFIG_FRAMECRC_MUXER)            += framecrcenc.o
 OBJS-$(CONFIG_GIF_MUXER)                 += gif.o
-OBJS-$(CONFIG_GIF_DEMUXER)               += gifdec.o
 OBJS-$(CONFIG_GSM_DEMUXER)               += raw.o
 OBJS-$(CONFIG_GXF_DEMUXER)               += gxf.o
 OBJS-$(CONFIG_GXF_MUXER)                 += gxfenc.o