Merge: src: remove some warnings and do some cleaning

Extracted from the first version of #817

Pull-Request: #819
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --cc src/ffi/java.nit
Simple merge

diff --cc src/interpreter/naive_interpreter.nit
Simple merge

diff --cc src/semantize/auto_super_init.nit
Simple merge

diff --cc src/semantize/typing.nit
Simple merge