0.9.15.15:

0.9.15.15:
	Fix bug #339c: INVALID-METHOD-ERROR from methods not matching
	any method group.
	... I'm actually not convinced by this fix: I think the method
		combination itself should probably call I-M-E, rather
		than have the effective method call it (see CLHS on
		INVALID-METHOD-ERROR); however, at the moment, given
		PRECOMPUTE-EFFECTIVE-METHOD's behaviour, this is the
		only way to signal the error at the right time.  Revisit
		when/if effective-method precomputation is adjusted.