Use symbolic names for popup menu ids in wxEVT_MENU_HIGHLIGHT events in wxMSW.

Use symbolic names for popup menu ids in wxEVT_MENU_HIGHLIGHT events in wxMSW.

No real changes, just use wxID_NONE instead of hardcoded -1 (in one place) and
-3 (in another one). Hardcoding them not only made the code less readable but
also resulted in two numbers actually becoming different when they almost
certainly were meant to be the same.

This shouldn't result in any changes in the user-visible behaviour but we now
avoid searching the menu bar for menu items with id of -1 needlessly.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64103 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775