pthread: include sys/types.h before sys/sysctl.h

Fixes compilation on FreeBSD with clang 3.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/pthread.c

@@ -37,8 +37,8 @@
 #elif HAVE_GETSYSTEMINFO
 #include <windows.h>
 #elif HAVE_SYSCTL
-#include <sys/sysctl.h>
 #include <sys/types.h>
+#include <sys/sysctl.h>
 #endif
 
 #include "avcodec.h"