Don't cast GPS times to float when writing segments to LIGO_LW
This PR fixes a precision issue when writing segments to LIGO_LW
XML format. Casting to float
loses precision compared to LIGOTimeGPS
. I think this was an issue when attempting to cast directly from numpy.float64
to glue.lal.LIGOTimeGPS
, but we don't use the glue
object any more, so this shouldn't be a problem any more.