Ignore WM_CLOSE generated by wxMSW edit control when Escape is pressed.

Ignore WM_CLOSE generated by wxMSW edit control when Escape is pressed.

Multiline edit control posts WM_CLOSE to its parent window when Escape key is
pressed inside it for some reason. This is unwanted as it totally bypasses our
logic for only closing the dialog when Escape is pressed if there is a
Cancel-like button in it, so suppress this behaviour by not letting the edit
control to get Escape at all.

Closes #12501.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68351 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775