Use the same logic for closing dialogs as for handling Escape key.

Use the same logic for closing dialogs as for handling Escape key.

Pressing "Esc" key closed the dialog with only wxID_OK button (but no
wxID_CANCEL one) by default but pressing the "close window" button only closed
it if wxID_CANCEL was present.

Fix this by using the same code in OnCloseWindow() as in OnCharHook(), after
extracting it into the new SendCloseButtonClickEvent() method.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65488 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775