Prepare an update for new C# changes

[michaelblyons]

See sublimehq/Packages#4547

[michaelblyons]

@keith-hall Was there a reason we had HTML comments instead of Razor comments as the marker in the syntax tests?

HTML comments in some spots seem to break downstream highlighting, and I'd like to know if that's a concern.

@do
<!-- HTML comment here detaches the block below from this `do` -->
{
    <p>forever</p>
} while(true)

Edit: Fixed.

[keith-hall]

I don't remember there being a compelling reason for using HTML comments, I think it should be fine to switch