Move the Digest/Sign split for SignatureAlgorithms to a lower level.

In order to delay the digest of the handshake transcript and unify
around message-based signing callbacks, a copy of the transcript is kept
around until we are sure there is no certificate authentication.

This removes support for SSL_PRIVATE_KEY_METHOD as a client in SSL 3.0.

Change-Id: If8999a19ca021b4ff439319ab91e2cd2103caa64
Reviewed-on: https://boringssl-review.googlesource.com/8561
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index 641b94a..627c288 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -4655,6 +4655,7 @@
 #define SSL_R_X509_VERIFICATION_SETUP_PROBLEMS 249
 #define SSL_R_SHUTDOWN_WHILE_IN_INIT 250
 #define SSL_R_INVALID_OUTER_RECORD_TYPE 251
+#define SSL_R_UNSUPPORTED_PROTOCOL_FOR_CUSTOM_KEY 252
 #define SSL_R_SSLV3_ALERT_CLOSE_NOTIFY 1000
 #define SSL_R_SSLV3_ALERT_UNEXPECTED_MESSAGE 1010
 #define SSL_R_SSLV3_ALERT_BAD_RECORD_MAC 1020