add test case for unterminated """ string

add test case for unterminated """ string

A directive that contains an unterminated """ string should not
cause each word of the string to be treated as a bare word. Instead,
the directive should fail to parse.

There are two tests. One just checks that a complete directive
containing such a string fails to parse. The other checks for a case
where a directive ends with a very long unterminated """ string,
and the directive is itself not closed. While this test won't fail,
it does trigger a nasty perl warning.