Display model: Try to provide the correct background color for transparent text drawing (#6844)
* GDI hooks: In the TextOut and ExtTextOut functions, get the previous color at the provided X, Y coordinates before calling the original function, so we at least have a chance of knowing the correct background color if the text is being drawn in transparent mode. This is necessary to detect highlighted text in some parts of Dragon NaturallySpeaking.
Fixes #6467