lib/hash: HashCollection::N become a virtual type

Signed-off-by: Jean Privat <jean@pryen.org>
examples/rosettacode: update ab to not crash on tests

Signed-off-by: Jean Privat <jean@pryen.org>
compiler: resolve types when doing new NativeArray

Signed-off-by: Jean Privat <jean@pryen.org>
tests: update sav because line changes in std/array.nit

Signed-off-by: Jean Privat <jean@pryen.org>