signal: interrupt_syscall is called by the core executing the thread that recieved the signal.

refs #999

kernel/include/process.h

@@ -437,6 +437,7 @@ struct sig_pending {
 	sigset_t sigmask;
 	siginfo_t info;
 	int ptracecont;
+	int interrupted;
 };
 
 typedef void pgio_func_t(void *arg);