1. wxTextCtrl::SetBackgroundColour() now works

1. wxTextCtrl::SetBackgroundColour() now works
2. wxListBox::SetBackgroundColour() now does something, although still not
   what I'd like
3. wxColour() now has a ctor from "const char *" to allow calls like
   SetBackgroundColour("green");
4. controls sample modified to use colors

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@872 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775