Add missing include of signal.h in virnetsocket.c

virNetSocketFree uses kill(SIGTERM) so we must include
signal.h for the definitions

* src/rpc/virnetsocket.c: Include signal.h

src/rpc/virnetsocket.c

@@ -27,6 +27,7 @@
 #include <sys/socket.h>
 #include <unistd.h>
 #include <sys/wait.h>
+#include <signal.h>
 
 #ifdef HAVE_NETINET_TCP_H
 # include <netinet/tcp.h>