Fingerprint level code cleanup.

Simplify the matching logic, by adding the fingerprint digests (that
match either the certificate or its public key) twice: once as a
cert digest, and again as a pkey digest.  This also avoids making
the new tafile support (where we know what's a cert and what's a
pkey) needlessly imprecise.

20131130

	Cleanup: simplify fingerprint security level implementation
	in new DANE code.  Viktor Dukhovni.  Files: src/tls/tls.h
	src/smtp/smtp_tls_policy.c src/tls/tls_dane.c
	src/posttls-finger/posttls-finger.c.