[m-rev.] for post commit review: bump the minimum requirements for the C# backend

[Peter Wang]

On Wed, 3 Jan 2018 22:50:43 -0500 (EST), Julien Fischer <jfischer at opturion.com> wrote:
> 
> For post-commit review.
> 
> (Note: I will update the configure script separately.)
> 
> -----------------------
> 
> Bump the minimum requirements for the C# backend.
> 
> README.CSharp:
>      Require at least version 4.5 of the .NET framework (or
>      the equivalent version of Mono).
> 
>      Delete the bit about the aliases for the Mono C# compiler.
>      As of Mono 2.11, mcs is the only one we need be concerned with.

That's fine.

Peter