Remove broken BC code in Registry

[Art4]

While working on the Registry class I noted this BC code that actually never worked. It was introduced in f6e63e6 (version 1.3).

The code was intended to fix a BC break in the Locator::__construct() method. But because the switch looks for locator instead of (uppercase) Locator there was no chance to register a BC class that matches this requirement. Please note also the wrong lower case in $this->get_class('file') and $this->get_class('content_type_sniffer') that would always return null instead of a class name. Also I could not find any complaints about a BC break for the changed parameter in the Locator::__construct() method.

Therefor I propose to remove this BC code, that actually never worked.

[jtojnar]

Looks good – the only way this could work if someone used the Registry newly introduced in f6e63e6 with the legacy class and lowercase name $simplepie->registry->register('locator', $class, true). But as you noticed that is not possible, since the lowercase $type argument would not be a key in the Registry::$defaults property so registration would fail on not finding a parent class to check subclass relationship for.

[jtojnar]

Now, if only we could drop the other legacy alias:

5f107f3#diff-c09efaf19f27f39a1f6829e8ded114062e329cb15f8ce1d65f1f0a6c6bb159bd

Unfortunately, that one can be relied on externally so we would need to deprecate it first. While at it, we should probably also deprecate Simplepie::set_*_class() methods, since that is the place that legacy classes are registered.

[Art4]

Now, if only we could drop the other legacy alias:

5f107f3#diff-c09efaf19f27f39a1f6829e8ded114062e329cb15f8ce1d65f1f0a6c6bb159bd

I also thought about removing that, but since the whole Cache class is already deprecated, it won't bother me.

Unfortunately, that one can be relied on externally so we would need to deprecate it first. While at it, we should probably also deprecate Simplepie::set_*_class() methods, since that is the place that legacy classes are registered.

The Simplepie::set_*_class() methods are already deprecated since SimplePie 1.3, see the phpdoc template in https://github.com/simplepie/simplepie/blob/1.3/library/SimplePie.php#L887-L894
I will made that clearer in a future PR.

[mblaney]

thanks @Art4 good catch!