First part of fixes to make this work under MSW.

First part of fixes to make this work under MSW.

1. letters actually appear on the screen
2. Clear() works
3. Backspace/Delete in one line works too
4. breaking lines works
5. cursor is now a wxCaret
6. tons of other fixes

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@2652 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775