expose parsetree

[svstuff]

Expose the full parsetree somehow. Either just in Scala (somewhat suboptimal, since that makes it annoying to use it from other languages) or output as a machine readable format.

This is the number 1 priority issue. The other tasks, such as generating statistics or tag files etc can all be done by separate tools once the parsetree is available, whether that be an internal Scala API or a machine readable format.

[svstuff]

Parsetree is now output as a compressed XML. The preprocessor context list (file names, macro expansions) is not yet output, but this is fairly easy to do. Should probably output this as a separate xml file and have tokens in the parsetree include a "context id".