Add is_returned field to env. Complete VoidReturnStatement
Complete S.ReturnStatement
Complete S.ReturnStatement. Correctly handle return in CompoundStatement
UPDATE grammar: for-iterator can contain variable decl
Fully update If/While/ForStatements to handle is_returned and compound/single-line scoping better
Fix problems with ForStatement scoping
Complete S.ArrayIterator
More fix: for-loop scoping
Add in_loop flag to env. Checks continue/break statements