IDocument: Reduce size of IDocument structure by reordering elements

On 64bit machines it should now have 48byte instead of 64.
Change-Id: I7a171864244e8faf26a2cf3c32abe9e705837fa3
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/coreplugin/idocument.cpp

@@ -80,12 +80,12 @@ public:
         delete infoBar;
     }
 
-    Id id;
     QString mimeType;
     Utils::FileName filePath;
     QString displayName;
     QString autoSaveName;
     InfoBar *infoBar;
+    Id id;
     bool temporary;
     bool hasWriteWarning;
     bool restored;