* wrap/python/spot.i (unblock_signal): New function.

* wrap/python/cgi/ltl2tgba.in (print_footer, alarm_handler)
(reset_alarm): New functions.  Kill the script and its
children if it runs for too long.
(render_dot): Call reset_alarm.

wrap/python/spot.i

@@ -30,6 +30,7 @@
 #include <iostream>
 #include <fstream>
 #include <sstream>
+#include <signal.h>
 
 #include "misc/version.hh"
 #include "misc/bddalloc.hh"
@@ -207,4 +208,13 @@ print_on(std::ostream& on, const std::string& what)
   on << what;
 }
 
+int
+unblock_signal(int signum)
+{
+  sigset_t set;
+  sigemptyset(&set);
+  sigaddset(&set, signum);
+  return sigprocmask(SIG_UNBLOCK, &set, 0);
+}
+
 %}