See https://github.com/libevent/libevent/pull/442

diff -u -r ../libevent-release-2.1.8-stable/include/event2/bufferevent_compat.h ./include/event2/bufferevent_compat.h
--- ../libevent-release-2.1.8-stable/include/event2/bufferevent_compat.h	2017-01-26 00:37:15.000000000 +0100
+++ ./include/event2/bufferevent_compat.h	2017-01-28 00:45:04.068858074 +0100
@@ -72,6 +72,7 @@
 	  error occurred
   @see bufferevent_base_set(), bufferevent_free()
   */
+EVENT2_EXPORT_SYMBOL
 struct bufferevent *bufferevent_new(evutil_socket_t fd,
     evbuffercb readcb, evbuffercb writecb, everrorcb errorcb, void *cbarg);
 
@@ -83,6 +84,7 @@
   @param timeout_read the read timeout
   @param timeout_write the write timeout
  */
+EVENT2_EXPORT_SYMBOL
 void bufferevent_settimeout(struct bufferevent *bufev,
     int timeout_read, int timeout_write);