Focus handling fixes - make sure new windows activate on show, ensure focus events...

Focus handling fixes - make sure new windows activate on show, ensure focus events call SetWindow with the previous / next focus window respectively, and go back to native behavior for now with acceptsFirstResponder until we can figure out how to pass the results of AcceptsFocus() to it without getting in a loop as the wx API calls native and vice versa.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@59467 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775