[patch] beginnings of the macro rewrite

[Joe Buck]

> And I'll bet rather highly that removing support for -traditional will break
> compilation of X or X apps that use imakefiles.

Yes, this is one of the main reasons why we cannot drop -traditional
(the Imakefile use plus many other inappropriate-but-well-established
misuses of the C preprocessor).

Don't worry, the issue is pretty much closed for now.