Fix: Ignore method named after reserved keywords

[localheinz]

This PR

• asserts that ClassFileLocator ignores methods named after reserved keywords when they have return type declarations
• adjusts ClassFileLocator

💁‍♂️ Ran into a weird issue when ClassFileLocator inspected something like

final class Foo
{
    public function class() : string
    {
        return self::class;
    }
}

on PHP 7.1 and reported two classes

• Foo
• string