size_t RSA_private_decrypt's input.

Change-Id: If05761052e235b38d9798b2fe4d8ba44293af891
Reviewed-on: https://boringssl-review.googlesource.com/5944
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/rsa.h b/include/openssl/rsa.h
index 2be50dc..e44e228 100644
--- a/include/openssl/rsa.h
+++ b/include/openssl/rsa.h
@@ -164,7 +164,7 @@
  *
  * WARNING: this function is dangerous because it breaks the usual return value
  * convention. Use |RSA_decrypt| instead. */
-OPENSSL_EXPORT int RSA_private_decrypt(int flen, const uint8_t *from,
+OPENSSL_EXPORT int RSA_private_decrypt(size_t flen, const uint8_t *from,
                                        uint8_t *to, RSA *rsa, int padding);
 
 /* RSA_message_index_PKCS1_type_2 performs the first step of a PKCS #1 padding