LibC: Fix strsignal() and implement psignal()

userspace/libraries/LibC/signal.cpp

@@ -1,5 +1,6 @@
 #include <BAN/Assert.h>
 #include <signal.h>
+#include <string.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 
@@ -10,6 +11,14 @@ int kill(pid_t pid, int sig)
 	return syscall(SYS_KILL, pid, sig);
 }
 
+void psignal(int signum, const char* message)
+{
+	if (message && *message)
+		fprintf(stderr, "%s: %s\n", message, strsignal(signum));
+	else
+		fprintf(stderr, "%s\n", strsignal(signum));
+}
+
 int raise(int sig)
 {
 	// FIXME: won't work after multithreaded