Fix compilation of timefilter test program.

The printf function is forbidden in library code, but not in test programs,
so #undefine the printf macro that disables the system printf function.
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavformat/timefilter.c

@@ -79,6 +79,8 @@ double ff_timefilter_update(TimeFilter *self, double system_time, double period)
 #include "libavutil/lfg.h"
 #define LFG_MAX ((1LL << 32) - 1)
 
+#undef printf
+
 int main(void)
 {
     AVLFG prng;