Use ascii_only_p() instead of ascii_only_
Use ascii_only_p() instead of ascii_only_

ascii_only_ does not usually have a correct value, so we ascii_only_p()
to make sure it does.

Related to #3531

kachick/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius,kachick/rubinius,kachick/rubinius,jsyeo/rubinius