OPENSSL_EXPORT SSL_CTX_set_keylog_bio.

Forgot to do that.

Change-Id: Ic7eb199c3acf4aa249be3f7a3312e8c2bc7a2372
Reviewed-on: https://boringssl-review.googlesource.com/1720
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index 66904fb..3838511 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -683,7 +683,7 @@
  *
  * The format is described in
  * https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format. */
-void SSL_CTX_set_keylog_bio(SSL_CTX *ctx, BIO *keylog_bio);
+OPENSSL_EXPORT void SSL_CTX_set_keylog_bio(SSL_CTX *ctx, BIO *keylog_bio);
 
 
 struct ssl_aead_ctx_st;