Start using Kconfig to configure SeaBIOS settings.

Create autoconf.h during the build.

Move a couple of config settings from config.h to Kconfig.
diff --git a/.gitignore b/.gitignore
index 3aa6a21..f9990fe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 out
 *.pyc
+.config
+.config.old