Rewrite DoPaint, FullPaint and add FullPaintDC to help deal with flicker problems and to be more like how the other Scintilla ports are working now.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70659 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/stc/stc.cpp

@@ -210,7 +210,7 @@ bool wxStyledTextCtrl::Create(wxWindow *parent,
     SetInitialSize(size);
 
     // Reduces flicker on GTK+/X11
-    SetBackgroundStyle(wxBG_STYLE_CUSTOM);
+    SetBackgroundStyle(wxBG_STYLE_PAINT);
 
     // Make sure it can take the focus
     SetCanFocus(true);