Implement navigation of macros through the new interface in ILanguageSupport.

Now, whenever you encounter a macro, you can:
- Jump to the position where it was defined
- See its body/signature and source-file in the navigation-widget
- See the preprocessed text that was yielded by the macro-use(including evaluation of the arguments of function-like macros).

Now you can finally easily see what exact code is created by all those function-like macros you use.