* src/sleep.c (main): Allow ERANGE since we allow "inf" values.
* src/timeout.c (parse_duration): Likewise.
* tests/misc/sleep.sh: New file. Tests for sleep(1).
* tests/misc/timeout-parameters.sh: Add case for newly allowed
$LDBL_MAX. Also use returns_ throughout the file. Also avoid
small timeout values which might give false failures under load.