New Configure option no-<cipher> (rsa, idea, rc5, ...).

crypto/rc4/rc4.h

diff --git a/crypto/rc4/rc4.h b/crypto/rc4/rc4.h
index 8d2b165..7418c2a 100644
--- a/crypto/rc4/rc4.h
+++ b/crypto/rc4/rc4.h
@@ -63,6 +63,10 @@
 extern "C" {
 #endif
 
+#ifdef NO_RC4
+#error RC4 is disabled.
+#endif
+
 #include <openssl/opensslconf.h> /* RC4_INT */
 
 typedef struct rc4_key_st