signal.h needed for kill(2)

Index: start/src/core/Instance.cpp
--- start/src/core/Instance.cpp.orig
+++ start/src/core/Instance.cpp
@@ -5,6 +5,7 @@
 
 #include <cstdlib>
 #include <cstring>
+#include <signal.h>
 #include <sys/poll.h>
 #include <sys/types.h>
 #include <sys/wait.h>
