Fix bug with using incorrect negative ids in wxEVT_MENU_HIGHLIGHT events.

Fix bug with using incorrect negative ids in wxEVT_MENU_HIGHLIGHT events.

wxMSW code implicitly cast ids carried by wxEVT_MENU_HIGHLIGHT events to
unsigned short so that they didn't compare equal to the (signed, negative) ids
of the real menu items. Because of this menu help strings were not shown for
any items with negative ids, i.e. those created using wxID_ANY.

Closes #11977.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64102 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775