- Add CefPostData::HasExcludedElements which returns true if the underlying

POST data includes elements that are not represented (issue #1761).
- Add CefRequest::SetReferrer and CefRequest::GetReferrer[URL|Policy]. The
  Referer value will no longer be stored in the header map.
- Move request-related conversion logic to CefRequestImpl and standardize the
  implementation.

libcef_dll/ctocpp/post_data_ctocpp.h

@@ -31,6 +31,7 @@ class CefPostDataCToCpp
 
   // CefPostData methods.
   bool IsReadOnly() OVERRIDE;
+  bool HasExcludedElements() OVERRIDE;
   size_t GetElementCount() OVERRIDE;
   void GetElements(ElementVector& elements) OVERRIDE;
   bool RemoveElement(CefRefPtr<CefPostDataElement> element) OVERRIDE;