LibC: Added missing signal flags

Added missing signal flags to signal.h

Libraries/LibC/signal.h

@@ -44,6 +44,13 @@ extern const char* sys_siglist[NSIG];
 #define SA_NOCLDSTOP 1
 #define SA_NOCLDWAIT 2
 #define SA_SIGINFO 4
+#define SA_ONSTACK 0x08000000
+#define SA_RESTART 0x10000000
+#define SA_NODEFER 0x40000000
+#define SA_RESETHAND 0x80000000
+
+#define SA_NOMASK SA_NODEFER
+#define SA_ONESHOT SA_RESETHAND
 
 #define SIG_BLOCK 0
 #define SIG_UNBLOCK 1