Using the $callable() syntax when used with a string of
the form 'Class::method' would error as an undefined
function, even if the string passed is_callable() or the
callable type-hint. The fix adds support for the $callable()
syntax for any string accepted by is_callable() or the
callable type-hint.
Fix bug 68475 test with deprecated notice
Reduced scope of unit test.
Added tests with arguments.
