New modular directory structure: parsers, preprocs, and outfmts.

New modular directory structure: parsers, preprocs, and outfmts.
Moved token.l.in, bison.y.in, and gen_instr.pl to parsers/nasm/.
New parser, preproc, and outfmt structures.  None are complete; outfmt
needs the most work.
The raw preprocessor added (for no preprocessing).
Currently the default for the nasm parser is to use the raw preproc; this
should be changed to nasm_preproc once the nasm preprocessor is finished.
A dbg output format is also new; because outfmt isn't done yet, there's not
much implementation.
What structures still need creating: listfmt, debugfmt.

svn path=/trunk/yasm/; revision=133