0.8.4.5:

0.8.4.5:
	PPC build fix (kludge)
	... use offsetof() to find where the glibc maintainers have put
		the uc_mcontext slot today, and delegate to appropriate
		source code
	non-x86/linux build fix
	... undefine arch_os_get_current_thread() from individual
		architecture header files
	Everywhere clean.sh fix
	... only include src/runtime/Config in tools-for-build/Makefile
		if it exists.  Now clean.sh works on a clean tree.