Replace sconfig with a C implementation.

Replace sconfig with a C implementation.
(smaller, faster, standard parser generator, no more python)

Provide precompiled parser, so bison and flex are optional dependencies.

Adapt Makefile and abuild (which uses some sconfig file as a
magic path) to match.

Drop python as dependency from README, and add bison and flex
as optional dependencies

Signed-off-by: Patrick Georgi <patrick.georgi@coresystems.de>
Acked-by: Stefan Reinauer <stepan@coresystems.de>
Acked-by: Ronald G. Minnich <rminnich@gmail.com>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5373 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1