Fix 'make depend' for libpostproc.

Originally committed as revision 6238 to svn://svn.ffmpeg.org/ffmpeg/trunk

Makefile

@@ -204,6 +204,9 @@ depend: .depend
 	$(MAKE) -C libavutil   depend
 	$(MAKE) -C libavcodec  depend
 	$(MAKE) -C libavformat depend
+ifeq ($(CONFIG_PP),yes)
+	$(MAKE) -C libpostproc depend
+endif
 ifeq ($(BUILD_VHOOK),yes)
 	$(MAKE) -C vhook       depend
 endif

libpostproc/Makefile

@@ -20,6 +20,8 @@ CFLAGS  = -I.. -I$(SRC_PATH)/libavcodec $(OPTFLAGS)
 
 include $(SRC_PATH)/common.mak
 
+depend: postprocess.c
+
 ifeq ($(BUILD_SHARED),yes)
 postprocess_pic.o: postprocess.c
 	$(CC) -c $(CFLAGS) -fomit-frame-pointer -fPIC -DPIC -o $@ $<