Teach crypto/x509 how to verify an Ed25519 signature.

BUG=187

Change-Id: I5775ce0886041b0c12174a7d665f3af1e8bce511
Reviewed-on: https://boringssl-review.googlesource.com/14505
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/x509.h b/include/openssl/x509.h
index 88455dd..44b3b7b 100644
--- a/include/openssl/x509.h
+++ b/include/openssl/x509.h
@@ -1246,5 +1246,6 @@
 #define X509_R_WRONG_LOOKUP_TYPE 133
 #define X509_R_WRONG_TYPE 134
 #define X509_R_NAME_TOO_LONG 135
+#define X509_R_INVALID_PARAMETER 136
 
 #endif