Namelist read from stdin

[Harald Anlauf]

Dear all,

namelist read from stdin (unit 5) mostly works as from file,
but I've found a case where the reading seems to get confused
during error recovery.  This may lead to skipped (lost) namelists.

This seems clearly restricted to unit 5, and requires that a
badly formatted namelist is encountered, otherwise it is fine.

Is this due to lack of or issues with buffering of STDIN?
GFORTRAN_UNBUFFERED_PRECONNECTED=y/n does not seem to have any
influence.

Is there something trivial I've overlooked?  Otherwise I'll prepare
a PR.

Thanks,
Harald