Allow duplicate variable names when platform-conditionalized

[KeyWorksRW]

Description:

It's possible to want to use a two platform specific controls that use the same variable name. That's currently not possible, because our unique variable is not checking platform conditionals. I encountered that when trying to use a wxButton on Windows and wxCommandLinkButton on Linux. I think this is going to be a rare occurrence, so it's definitely a low priority, but it should be looked into at some point.