Fix is_callable $callable_name for anon class methods

[adsr]

Fixes bug https://bugs.php.net/bug.php?id=73118

This patch aims to make is_callable return a usable $callable_name for anonymous class methods. Anon class methods are formatted like...

class@anonymous\x00/path/to/script.php0xdeadbeef::funcName

...where \x00 is a null-char. The current behavior is to return just "class@anonymous" which is unusable as a function ref, e.g., as a parameter to call_user_func.

I attempt to preserve back-compat by only returning the full callable name (including null-char) when the function actually exists (retval is TRUE and $syntax_only is FALSE).

Open to suggestions if someone can think of a cleaner way.

EDIT: See nikic's comment below and new commit.

[nikic]

I'd be in favor of just always returning the name as-is. As the comment indicates, the current implementation was just used because it happened to be how PHP 5 behaved (by accident, not by design). Now that there is a specific reason why this behavior is not desirable, we should just drop it.

[adsr]

If nothing relies on the truncating behavior, that sounds good to me. I will change tests and update PR.

[nikic]

Merged via 7e5cf2a, thanks!

[nikic]

Also made run-tests fail on BORKED tests in 981c587. The Travis build should not have been passing on this PR.