[UXTHEME] -Rename WND_CONTEXT to WND_DATA to avoid confusion with the DRAW_CONTEXT. The WND_DATA is information valid throughout the life of a window and DRAW_CONTEXT is information throughout a draw operation in the non client area of the window.
[UXTHEME] -Fix the tab background pattern hack when the background pattern is smaller than the window that we are trying to paint. CORE-13147, CORE-13192. There is still a bug where the pattern doesn't change after a theme change.