[Development] right-to-left mode on Mac

[René J.V. Bertin]

Hi Gabriel,

I've taken a quick first look at implementing right-to-left support in contextmenus and think it's going to be quite tricky getting the alignment right - a process of educated trial and educating error :)
Adding R2L support to my code rendering texted separators was trivial (https://github.com/RJVB/osx-integration/commit/a6ca7482e2ffe3c25a82f80312e7b8326b167a1f), but for other menu items the point relative to which right-alignment takes place depends on factors I haven't yet understood.

The shortcut mnemonics are a different problem, they're drawn as a string, and the drawing routine will print them in reverse when R2L mode is selected. Probably not the aspect to focus on first and maybe not even that big a deal to leave "as is" (in fact, I don't understand why Apple doesn't invert shortcut representations, obliging users to change their reading direction to parse the indication in the order they'd be entering it.

Cheers,
René