prevent infinite recursion in impossible

include/decl.h

@@ -152,6 +152,10 @@ E NEARDATA struct sinfo {
 	int panicking;		/* `panic' is in progress */
 #if defined(VMS) || defined(WIN32)
 	int exiting;		/* an exit handler is executing */
+#endif
+	int in_impossible;
+#ifdef PANICLOG
+	int in_paniclog;
 #endif
 } program_state;