No changes, just slightly simplify the tool insertion code.

No changes, just slightly simplify the tool insertion code.

Added a helper DoInsertNewTool() function to avoid code duplication and ensure
that we never forget to delete a new tool if inserting it into the toolbar
failed.

Also explicitly document that the tool passed to the public InsertTool() is
not owned by the toolbar and so must be deleted by the caller if its insertion
failed.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62846 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775