Add SSL_get_rc4_state.

This allows the current RC4 state of an SSL* to be extracted. We have
internal uses for this functionality.

Change-Id: Ic124c4b253c8325751f49e7a4c021768620ea4b7
Reviewed-on: https://boringssl-review.googlesource.com/3722
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/rc4.h b/include/openssl/rc4.h
index b5fc8ed..42a74f2 100644
--- a/include/openssl/rc4.h
+++ b/include/openssl/rc4.h
@@ -66,12 +66,10 @@
 
 /* RC4. */
 
-
-typedef struct rc4_key_st {
+struct rc4_key_st {
   uint32_t x, y;
   uint32_t data[256];
-} RC4_KEY;
-
+} /* RC4_KEY */;
 
 /* RC4_set_key performs an RC4 key schedule and initialises |rc4key| with |len|
  * bytes of key material from |key|. */