add wxEVT_COMMAND_HEADER_SEPARATOR_DCLICK and semi-automatic header resizing support

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57186 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/headerctrlg.h

@@ -68,9 +68,12 @@ private:
     // return the horizontal start position of the given column
     int GetColStart(unsigned int idx) const;
 
-    // refresh the given column [only]
+    // refresh the given column [only]; idx must be valid
     void RefreshCol(unsigned int idx);
 
+    // refresh the given column if idx is valid
+    void RefreshColIfNotNone(unsigned int idx);
+
     // refresh all the controls starting from (and including) the given one
     void RefreshColsAfter(unsigned int idx);