Fix bug #79349: Unlinked anonymous classes prevent using preloading

[nikic]

Check the opcodes of preloaded classes for references to anonymous classes and force them to be linked. This prevents "Anonymous class wasn't preloaded" fatal errors at runtime.

This is a partial fix, because the same problem also exists for other dynamically declared classes. In that case the fix would be more complicated, as we would have to "link" the class but keep it under the RTD key, and then at runtime only do the bucket key change (or possibly, in this case, actually insert it as a new HT entry, as it would be hard to reset the bucket name after the request). Because of this I'm only fixing the more important anon class case for now.

[nikic]

I've pushed a second commit with a possible fix for the general dynamic class case.

One thing to note here is that these changes do require the deps of dynamically declared classes to exist, which may be problematic in some cases. The escape hatch is to make the dynamic declaration at the top level, not inside a function / method, then we won't preload it. I think that's what people already do anyway.

[nikic]

Closing this in favor of #5260.