Add some debugger memory utilities (#109)

* add some memory utilities

* run waitpid in a separate thread and support very simple breakpoints

* fix breakpoints

* add missing windows stub function

* fix error message on exit

game/kernel/kscheme.cpp

@@ -7,6 +7,7 @@
 #include <cassert>
 #include "kscheme.h"
 #include "common/common_types.h"
+#include "common/goal_constants.h"
 #include "kmachine.h"
 #include "klisten.h"
 #include "kmalloc.h"