Change preprocessor parser to use pyparsing

[gnikit]

Description
The current preprocessor parser is flimsy and it does not work as expected

Describe the solution you'd like
Use pyparsing https://github.com/pyparsing/pyparsing for parsing the preprocessor instead of the manual parsing

[cafhach]

Is the speed of pyparsing adequate?

[gnikit]

@cafhach I would suspect so. I have no indication that pyparsing would cause any problems, but in general performance is not that important for a language server when you compare it with the maintenance cost of the parser