lib/math: Added bin_not function to Int

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
lib/standard/math: Fixed documentation on old binary operators

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
nitunit: accept an absolute path for `--dir`.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
Merge: lib/math: Added bin_not function to Int

Added missing function bin_not to `Int` as I might need it in the near future.

I figured it could be needed by someone else, so why not !

Pull-Request: #806
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Merge: nitunit: accept an absolute path for `--dir`.

When I passed an absolute path to the `--dir` option of `nitunit`, I got errors like this one:
```
ERROR: test_unread_order (in file /my/costum/dir/.nitunit/test_push_back_reader_TestPushBackDecorator_test_unread_order.nit): sh: 1: .//my/costum/dir/.nitunit/test_push_back_reader_TestPushBackDecorator_test_unread_order.bin: not found
```

It was a trivial bug so I fixed this.

Pull-Request: #809
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>