Export ssl_client_hello_init for fuzzers.

Chromium's fuzzer uses a shared library build.

Change-Id: I49a9fef9c0f10694302727d0251005240c30988f
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/46864
Reviewed-by: Adam Langley <agl@google.com>

ssl/internal.h

@@ -2113,7 +2113,10 @@ bool ssl_log_secret(const SSL *ssl, const char *label,
 
 // ClientHello functions.
 
-bool ssl_client_hello_init(const SSL *ssl, SSL_CLIENT_HELLO *out,
+// ssl_client_hello_init parses |body| as a ClientHello message, excluding the
+// message header, and writes the result to |*out|. It returns true on success
+// and false on error. This function is exported for testing.
+OPENSSL_EXPORT bool ssl_client_hello_init(const SSL *ssl, SSL_CLIENT_HELLO *out,
                                           Span<const uint8_t> body);
 
 bool ssl_client_hello_get_extension(const SSL_CLIENT_HELLO *client_hello,