New: CFHTTPRequest.js withCredential support to deliver cookies in CORS request

This is a modification to #2138.  In coordination with HMSimmonds, CFHTTPRequest was modified to not break against the ActiveXObject NativeRequest.

Also, CPURLConnection was modified to reduce the withCredentials flag to a file-scope member.  This has been done to facilitate use of withCredentials when a developer cannot modify the CPURLConnection manually (e.g. https://github.com/wireload/Ratatosk/blob/master/WLRemoteLink.j, line 466).

Refs #1296, #2138