Fix clicking on checkboxes in generic wxDataViewCtrl.

Back port the fix of r75329 from the trunk but without changing
GetEffectiveAlignment() visibility to avoid changing the ABI.

See #15731.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@75330 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775