cdtime and big hours

[doutriaux1]

import cdtime
val = 239261039241284857122685270850462023680.0
cdtime.reltime(val, "hours since 1").tocomp()

fails as follow:

CDMS error: Error on time conversion: invalid hour = 239261039241284857122685270850462023680.000000

Traceback (most recent call last):
  File "/git/uvcdat/testing/cdms2/test_long_hour.py", line 5, in <module>
    cdtime.reltime(val, "hours since 1").tocomp()
Cdtime error: Invalid component time