Add HeapTest and make GC work enough to pass it

Change-Id: If06eaef2921b64b3226bfd347acaec60ec993e67
diff --git a/src/signal_catcher.cc b/src/signal_catcher.cc
index e6e423d..b83e71d 100644
--- a/src/signal_catcher.cc
+++ b/src/signal_catcher.cc
@@ -23,6 +23,7 @@
 #include <unistd.h>
 
 #include "heap.h"
+#include "runtime.h"
 #include "thread.h"
 #include "utils.h"