Merge: misc/vim: highlight the new Int literals

Add support for bin, oct and hex literals which are restrictive enough to detect invalid digits. Also accept `_` in all Int literals, and the suffixes `[iu]8|16|32` proposed by #1588.

Supports `_` in Float literals, it's not yet available but it can't be too far off.

Pull-Request: #1600
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>