Test fix for perls with OP_AELEMFAST_LEX
Const fix
Add get_kids() to subcall node

Allows the tree matching code to treat the node as an optree and recurse into
it trying to JIT its kids.
JIT array access ops

Supports aelemnfast and aelemfast_lex (completely); aelem semantics are mostly
supported, except:
- use uf reference as array index warning
- Perl malloc warp check
- localization of tied array elements using EXISTS/DELETE