Libdparse with DMD frontend

[Eugene Wissner]

libdparse was created at the time D frontend was written in a 
different language and wasn‘t available as a library.

The D frontend itself isn‘t allowed to adopt the latest D 
features straightaway, because it would make bootstrapping and 
porting to other compilers more complicated than it should be. So 
the frontend should be compilable with an older version of DMD. 
Furthermore it should be compatible with C++, so it can be used 
by GDC and LDC. Therefore DMD is not always pretty and might be 
not the best fit for the high level code and could profit from a 
high-level wrapper.

Can libdparse be such a wrapper? Updating libdparse would 
probably be less painful, because it doesn‘t need to reimplement 
the frontend.
Writing another "libdparse" is not desired because libdparse is 
used by such tools like D-Scanner and becomes actually useful if 
used by that tools.

It is a big change to libdparse, so I‘d like to know if something 
is wrong with it and if the work on it is welcome.