Clarify return values for EVP_DigestVerifyFinal.
Clarify return values for EVP_DigestVerifyFinal.

Previous language was unclear.  New language isn't pretty but I believe
it is more accurate.

Signed-off-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
Reviewed-by: Ben Laurie <73675debcd8a436be48ec22211dcf44fe0df0a64@openssl.org>
Reviewed-by: Richard Levitte <5fb523282dd7956571c80524edc2dccfa0bd8234@openssl.org>

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl