Preprocess CFG files

[Greno Zee]

To my big surprise search for "preprocess" returns no results - so here goes:

Would you guys feel like implementing preporvessing of the CFG files?
It would be great if one could specify on the command line multiple /define:XXXX switches and inside the CFG files

#ifdef
#elseifdef
#else
#endif

including some boolean login
& - and
| - or
! - not

It might seem unnecessery but I have now already several newgrf config files and whenever some common GRF file comes out, I add it to the one I currently play, then forget to update all the others and I'm in a stage where I in fact lost track of what GRFs actually are on my system and where they are used and where not.

I hope you see the potential of this feature

[Patchman]

Feel free to run the cfg through a C preprocessor before starting TTDPatch. I'm not going to write an even marginally competent preprocessor for parsing the cfg files.