in crypt-sha*, reject excessive rounds as error rather than clamping

in crypt-sha*, reject excessive rounds as error rather than clamping

the reference implementation clamps rounds to [1000,999999999]. we
further limited rounds to at most 9999999 as a defense against extreme
run times, but wrongly clamped instead of treating out-of-bounds
values as an error, thereby producing implementation-specific hash
results. fixing this should not break anything since values of rounds
this high are not useful anyway.