Complete rewrite of build infrastructure for toolchain.

	* build-toolchain.sh: Rewritten to support all new features
	requested by customers, except (in this verision) Canadian cross
	compilation.
	* component-versions: Created.
	* download-toolchain.sh: Put GCC infrastructure components in
	their own source directory.
	* get-versions.sh: Created.
	* rel-rpaths.sh: Created.
	* symlink-all: Deleted.
	* symlink-all.sh: Created.