Make Lua errors return current state

Lua expects the state to be as it is at the time of error so we must
return the current state. A call is not an atomic operation on the
state.
Add expression pseudo statement and use for repeat

The #expr_stmt{} pseudo statement wraps an expression and returns a
single value. #call_stmt{} also wraps an expression which is limited
to a cal returns multiple values.
Expressions return precisely single or multiple values

This will add new ?MULTIPLE instruction which generate multiple values
to code but it simplifies emulator.