Fix compilation with msvc/icl due to missing header and define.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_drawtext.c

@@ -26,10 +26,12 @@
  * filter by Gustavo Sverzut Barbieri
  */
 
+#include "config.h"
+#if HAVE_SYS_TIME_H
 #include <sys/time.h>
+#endif
 #include <time.h>
 
-#include "config.h"
 #include "libavutil/avstring.h"
 #include "libavutil/bprint.h"
 #include "libavutil/common.h"

libavutil/mathematics.h

@@ -45,6 +45,9 @@
 #ifndef M_PI
 #define M_PI           3.14159265358979323846  /* pi */
 #endif
+#ifndef M_PI_2
+#define M_PI_2         1.57079632679489661923  /* pi/2 */
+#endif
 #ifndef M_SQRT1_2
 #define M_SQRT1_2      0.70710678118654752440  /* 1/sqrt(2) */
 #endif