0.8.0.1:

0.8.0.1:
	Fix build on FreeBSD
	... don't #include <proc.h>, which defines a struct thread; (thanks
		to Henrik Motakef)
	... do sigaltstack() if #+c-stack-is-control-stack (which is, in
		practice, all the time).

	(this /may/ break building on OpenBSD, which uses the same OS-dependent
	routines; it is possible that OpenBSD needs something from <proc.h>;
	if so, we need to find some compromise)