Asn1 generalize time parsing fails if the second fractions are too large

[Tyrrx]

As of X.680 an ASN1 generalized time can have any number of second fractions (Section 46.2).

Example output: Error: Unrecognized time: 20260218092423.1706741Z

[lapo-luchini]

Fixed and added test case. Thanks for the heads-up!