Add macros hiding the ugly casts needed to pass wxStrings to Windows API functions and use them in a couple of places in wxBase to simplify the code. Closes #14338. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71636 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775