Add conditional build of strptime

Originally committed as revision 820 to svn://svn.ffmpeg.org/ffmpeg/trunk

libav/Makefile

@@ -13,9 +13,14 @@ OBJS= utils.o cutils.o allformats.o
 # mux and demuxes
 OBJS+=mpeg.o mpegts.o ffm.o crc.o img.o raw.o rm.o asf.o \
       avienc.o avidec.o wav.o swf.o au.o gif.o mov.o jpeg.o 
+# framehook.o
 # file I/O
 OBJS+= avio.o aviobuf.o file.o 
 
+ifeq ($(BUILD_STRPTIME),yes)
+OBJS+= strptime.o
+endif
+
 ifeq ($(CONFIG_VIDEO4LINUX),yes)
 OBJS+= grab.o
 endif