Revert "Merge pull request #473 from methodmissing/fix-engine-endpoint"

This reverts commit 1a18c7b0a8, reversing
changes made to bef9a41bdb.

src/stream_engine.hpp

@@ -132,7 +132,7 @@ namespace zmq
         options_t options;
 
         // String representation of endpoint
-        char *endpoint;
+        std::string endpoint;
 
         bool plugged;