Resolve compiler warning on FreeBSD.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@254801 65c4cc65-6c06-0410-ace0-fbb531ad65f3

addons/chan_ooh323.h

@@ -37,6 +37,7 @@
 #include <netdb.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <signal.h>
 #include <sys/signal.h>
 
 #include <asterisk/lock.h>