Compute the diff between the old EXPECTF and the new output and
don't touch lines that still match the old EXPECTF. This reduces
the amount of manual fixup necessary after running bless_tests.php.
Resources used as array keys are generally handled by throwing a
notice and converting the resource to the resource handle. The only
exception is the [$resource => null] syntax, where this was treated
as an illegal offset type instead. However, this also only happened
for VM evaluations, the AST evaluator did handle resources correctly.
