Better document warning suppression code
diff --git a/tinyxml2.cpp b/tinyxml2.cpp
index 5c91843..be949d7 100755
--- a/tinyxml2.cpp
+++ b/tinyxml2.cpp
@@ -1769,7 +1769,8 @@
     _errorStr2( 0 ),

     _charBuffer( 0 )

 {

-    _document = this;	// avoid warning about 'this' in initializer list

+    // avoid VC++ C4355 warning about 'this' in initializer list (C4355 is off by default in VS2012+)

+    _document = this;

 }