New new string

See merge request !30

String concat

See merge request !29

New string

See merge request !28

- expr add string: don't call valueOf if the argument is already a
string
- inside String.java, if it called it's own function 'length()', NameNode
didn't generate code, fixed that in NameNode:checkType

String concat

See merge request !27

Array subtype

See merge request !26

Master

See merge request !25