Print "File not found" error
Make `eq?` embedded function
Change code-walker to use return value for next instruction
Fix indent and load util.yl
Push call stack in `apply`
Enable optimizer
Save/restore arena in `modifyRestParams`
Use `match` function in optimizer
code-walker continues traversal when callback returns nil
Use `unless` instead of `when`
Make `not` inline and optimize its generated code
Add comment
Optimize simple reference
Make `GREF t` to `CONST t`