replace ASSERT_TRUE by ASSERT_NE in Base64 tests
generalize tests
fix digest finalization on non-Shortened digests

This commit fixes possible memory corruption and information leak
vulnearbility when generating non-Shortened (long) digests.

You will normally generate Shortened digest (not suffixed by `_long`)
and this is an error which occurs on non-standard configurations.
bump version to 3.0-rc9