Add bound checks for method indices

[mandolaerik]

No description provided.

[mandolaerik]

No tests yet, and I'm not sure this is the right approach. Opens:

• Need a cost analysis: how much does this bloat generated code?
  • In particular: I tried to design a fallback behaviour that minimizes the cost in code bloat, but at the cost of functionality (clearing all indices to zero is cheap but more rude than strictly necessary). Need some real numbers to assess if it's worth it.
• With this patch, the callee checks the bound; should it be the caller? That would give a better error message, but probably also more code bloat.
• How well does this generalize to other bound checks? e.g., accessing params or session variables in object arrays, or creating traitrefs to object arrays.

[syssimics]

Verification #12297543: fail