try.in - check also for is_nanl availability
t/abs.t - modify for unavailability of nanl/isnanl
t.nan_pow.t - cater for presence of nan**0 bug
t/overload.t - modify test 23 in case nan**0 bug is present
Makefile.PL - run compiler check for availability of isnanl
LongDouble.pm - update docs
LongDouble.xs - cater for absence of nanl/isnanl
Changes - update