FFmpeg uses -D_ISOC9X_SOURCE and not -D_GNU_SOURCE in CFLAGS.

Originally committed as revision 20057 to svn://svn.mplayerhq.hu/mplayer/trunk/libswscale

libswscale/Makefile

@@ -10,7 +10,7 @@ endif
 # NOTE: -I.. is needed to include config.h
 CFLAGS=-I.. -I$(SRC_PATH) -I$(SRC_PATH)/libavutil $(OPTFLAGS) \
        -DHAVE_AV_CONFIG_H -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE \
-       -D_GNU_SOURCE
+       -D_ISOC9X_SOURCE
 
 OBJS= swscale.o rgb2rgb.o yuv2rgb.o
 ifeq ($(TARGET_ALTIVEC),yes)