File s2/unit/003-000-string-ops.s2 artifact f6ea078169 part of check-in 0ab8c75c49

assert 'ab' === 'a'+"b";
assert 'a123' === 'a' + 123;
assert 123 === 123 + 'a';
assert '123' === '1' + 2 + 3;
assert 123 === +'1' + 122;
assert 'def' === 'd'+<<<X e X+"f";