Show opcode in error message for debug
Stop using macros before their definition
Rename set functions more general name

`set-union` => `union`
`set-intersect` => 'intersect`
Fix `if` not to accept multiple forms and add `cond`
Rename `let` to `let1`
Rename `with` to `let`
Add named-let and rename `awith` to `alet`
Fix indent
Remove `def` macro and add `defun` macro
Rename file extension from arc to yl
Merge branch 'feature/cl' into develop