Added arcfour crypto.

test/unit/stdlib/crypto/rc4.c3

@@ -0,0 +1,16 @@
+import std::crypto;
+import std::io;
+
+fn void! rc_crypt() @test
+{
+	Rc4 rc;
+	rc.init(&&x"63727970746969");
+	char[200] x;
+	char[] text = "The quick brown fox jumps over the lazy dog.";
+	rc.crypt(text, &x);
+	char[*] res = x"2ac2fecdd8fbb84638e3a4
+	                820eb205cc8e29c28b9d5d
+	                6b2ef974f311964971c90e
+	                8b9ca16467ef2dc6fc3520";
+	assert(res[:text.len] == x[:text.len]);
+}