No real changes, just minor cleanup in Cocoa wxDataViewCtrl.

No real changes, just minor cleanup in Cocoa wxDataViewCtrl.

Start cleaning up Cocoa wxDataViewCtrl implementation:
 - Don't use "this->" which is not used anywhere else in wx code.
 - Use "()" instead of "(void)" as per wx coding standards.
 - Don't use end of function comments, this is inconsistent and
   unmaintainable.

No real changes otherwise.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62384 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775