fix(ssl): export ssl_handshake_new and tls12_check_peer_sigalg

The shared-library ssl_test build failed to link against libssl.so
because the previous commit's MLDSAHandshakeTest.RejectedByPeerSigalgCheckInTLS12
calls these internal symbols directly. Mark them OPENSSL_EXPORT (along
with the SSL_HANDSHAKE ctor/dtor used by UniquePtr) so they are visible
in shared builds.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dkostic

ssl/internal.h

@@ -1842,8 +1842,8 @@ struct SSL_HANDSHAKE_HINTS {
 };
 
 struct SSL_HANDSHAKE {
-  explicit SSL_HANDSHAKE(SSL *ssl);
-  ~SSL_HANDSHAKE();
+  OPENSSL_EXPORT explicit SSL_HANDSHAKE(SSL *ssl);
+  OPENSSL_EXPORT ~SSL_HANDSHAKE();
   static constexpr bool kAllowUniquePtr = true;
 
   // ssl is a non-owning pointer to the parent |SSL| object.
@@ -2203,7 +2203,7 @@ struct SSL_HANDSHAKE {
 // so many tickets.
 constexpr size_t kMaxTickets = 16;
 
-UniquePtr<SSL_HANDSHAKE> ssl_handshake_new(SSL *ssl);
+OPENSSL_EXPORT UniquePtr<SSL_HANDSHAKE> ssl_handshake_new(SSL *ssl);
 
 // ssl_check_message_type checks if |msg| has type |type|. If so it returns
 // one. Otherwise, it sends an alert and returns zero.
@@ -2486,8 +2486,9 @@ bool tls12_add_verify_sigalgs(const SSL_HANDSHAKE *hs, CBB *out);
 // tls12_check_peer_sigalg checks if |sigalg| is acceptable for the peer
 // signature. It returns true on success and false on error, setting
 // |*out_alert| to an alert to send.
-bool tls12_check_peer_sigalg(const SSL_HANDSHAKE *hs, uint8_t *out_alert,
-                             uint16_t sigalg);
+OPENSSL_EXPORT bool tls12_check_peer_sigalg(const SSL_HANDSHAKE *hs,
+                                            uint8_t *out_alert,
+                                            uint16_t sigalg);
 
 
 // Underdocumented functions.