one successful return type. simplify build on vs2015
diff --git a/tinyxml2.h b/tinyxml2.h
index a0d2693..c6a1f87 100755
--- a/tinyxml2.h
+++ b/tinyxml2.h
@@ -485,7 +485,6 @@
 // WARNING: must match XMLDocument::_errorNames[]

 enum XMLError {

     XML_SUCCESS = 0,

-    XML_NO_ERROR = 0,

     XML_NO_ATTRIBUTE,

     XML_WRONG_ATTRIBUTE_TYPE,

     XML_ERROR_FILE_NOT_FOUND,

@@ -1673,7 +1672,7 @@
 

     /// Return true if there was an error parsing the document.

     bool Error() const {

-        return _errorID != XML_NO_ERROR;

+        return _errorID != XML_SUCCESS;

     }

     /// Return the errorID.

     XMLError  ErrorID() const {