Index more class references

[YanisBft]

Until now, Enigma only indexed class references through constructor methods. With this PR, it now indexes class references in 3 more ways:

• When used in instanceof
• When used in a cast
• When the class itself is called (MyClass.class), which fixes #26

[liach]

Should we consider checkcast instruction as well?

[YanisBft]

Should we consider checkcast instruction as well?

Good idea, now done

[Juuxel]

Hmm, checkcast would catch some of the "invisible" casts done for generic objects, like when getting an element from a list with a specific type

[YanisBft]

Hmm, checkcast would catch some of the "invisible" casts done for generic objects, like when getting an element from a list with a specific type

These casts are invisible with Procyon, but seem to appear with CFR. Should I revert?

[Juuxel]

I don't think it's a huge issue. The generics checkcasts are references to that type after all :smile:

[LlamaLad7]

Why care about the specific opcodes rather than just considering every TypeInsnNode?