Don't leak wxDataViewCtrl column objects in wxOSX/Cocoa.

NSOutlineView addTableColumn method takes ownership of the column passed to
it, so we must release it ourselves to avoid leaking it.

Closes #16223.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76636 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -677,6 +677,7 @@ wxOSX:
 - Implement support for wxGA_VERTICAL in wxGauge (themindiswatching).
 - Add support for wxEVT_COMBOBOX_DROPDOWN and wxEVT_COMBOBOX_CLOSEUP
   events to wxOSX/Cocoa (Igor Korot).
+- Fix several memory leaks in wxDataViewCtrl (John Roberts).
 
 
 3.0.0: (released 2013-11-11)

src/osx/cocoa/dataview.mm

@@ -2045,6 +2045,10 @@ bool wxCocoaDataViewControl::InsertColumn(unsigned int pos, wxDataViewColumn* co
     // specified position the column is first appended and - if necessary -
     // moved to its final position:
     [m_OutlineView addTableColumn:nativeColumn];
+
+    // it is owned, and kepy alive, by m_OutlineView now
+    [nativeColumn release];
+
     if (pos != static_cast<unsigned int>([m_OutlineView numberOfColumns]-1))
         [m_OutlineView moveColumn:[m_OutlineView numberOfColumns]-1 toColumn:pos];