CVE-2024-43380: fugit parse and parse_nat stall on lengthy input

The fugit “natural” parser, that turns “every wednesday at 5pm” into “0 17 * * 3”, accepted any length of input and went on attempting to parse it, not returning promptly, as expected. The parse call could hold the thread with no end in sight.

Fugit dependents that do not check (user) input length for plausability are impacted.