Remove rc4() wrapper

This is not really of that much use since rc4_skip() can be used as
easily. In addition, rc4 has caused some symbol conflicts in the past,
so it is easier to live without that as an exported symbol.

src/crypto/ms_funcs.c

@@ -404,7 +404,7 @@ int encrypt_pw_block_with_password_hash(
 	 */
 	pos = &pw_block[2 * 256];
 	WPA_PUT_LE16(pos, password_len * 2);
-	rc4(pw_block, PWBLOCK_LEN, password_hash, 16);
+	rc4_skip(password_hash, 16, 0, pw_block, PWBLOCK_LEN);
 	return 0;
 }