DolphinWX: Move the CodeView debugger view over to wxGraphicsContext

This is a more advanced drawing 'backend' over the previous one and allows us to control things like transparency and anti-aliasing, etc.
DolphinWX: Parenthesize some expressions in CodeView.cpp
Merge pull request #865 from lioncash/debugger-stuff

DolphinWX: Use wxGraphicsContext in the Code View for the debugger.