new target ./setup plain_source?

[Marc Weber]

Hi.

What about adding another target ./setup plain_source which should
preprocess everything (including cpp) and output the files to an extra
directory?
Why?
This could be used for haddock documentation generation (Not sure how
this is done) and perhaps to be read by future IDE's to provide compiler
independent completion etc?

eg ./setup haddock on haddock sources itself fails on line

  #if defined(mingw32_HOST_OS)
...

What do you think?

Marc Weber