include sys/select.h to get select, according to posix 2001,

fix compilation on freebsd 5.5

Originally committed as revision 15406 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/tcp.c

@@ -22,6 +22,7 @@
 #include <unistd.h>
 #include "network.h"
 #include "os_support.h"
+#include <sys/select.h>
 #include <sys/time.h>
 
 typedef struct TCPContext {