changes 'make' in a couple places to $(MAKE) patch by ("Steven M. Schultz" <sms 2bsd com>)

Originally committed as revision 3988 to svn://svn.ffmpeg.org/ffmpeg/trunk

Makefile

@@ -168,10 +168,10 @@ installlib:
 dep:	depend
 
 depend: .depend
-	make -C libavcodec depend
-	make -C libavformat depend
+	$(MAKE) -C libavcodec depend
+	$(MAKE) -C libavformat depend
 ifeq ($(BUILD_VHOOK),yes)
-	make -C vhook depend
+	$(MAKE) -C vhook depend
 endif
 
 .depend: $(SRCS)