0.6.12.4:

0.6.12.4:
	made grovel-headers.c run automatically as part of the build
		process (so that the automatically-generated file
		output/stuff-groveled-from-headers.lisp replaced the
		old symlink src/code/target-os-types.lisp)
	redid grovel_headers.c DEFCONSTANT macro as function
	removed 'ln -sf $sbcl_arch-linux-types.lisp' stuff (from
		src/runtime/make-config.sh??)
	redid the definition of a stem in stems-and-flags.lisp,
		as a relative path from SBCL base directory instead
		of from the src/ subdirectory, so that it can now
		refer to "output/stuff-groveled-from-headers.lisp