vm: remove half-assed signal queueing scaffolding

Should implement it right later. See #297.

vm/os-unix.cpp

@@ -148,8 +148,9 @@ void factor_vm::dispatch_signal(void *uap, void (handler)())
 
 void factor_vm::enqueue_safepoint_signal(cell signal)
 {
-	sigaddset(&safepoint_signals, signal);
+	/* to be implemented, see #297
 	code->guard_safepoint();
+	*/
 }
 
 void memory_signal_handler(int signal, siginfo_t *siginfo, void *uap)

vm/vm.cpp

@@ -20,9 +20,6 @@ factor_vm::factor_vm() :
 	last_nano_count(0),
 	signal_callstack_seg(NULL)
 {
-#ifndef WINDOWS
-	sigemptyset(&safepoint_signals);
-#endif
 	primitive_reset_dispatch_stats();
 }
 

vm/vm.hpp

@@ -725,7 +725,6 @@ struct factor_vm
 	void dispatch_signal(void *uap, void (handler)());
 	void enqueue_safepoint_signal(cell signal);
 	void unix_init_signals();
-	sigset_t safepoint_signals;
   #endif
 
   #ifdef __APPLE__