Remove switch case fallthrough

[David Gileadi]

On 5/14/21 12:39 PM, Ogi wrote:
> On Thursday, 13 May 2021 at 14:25:53 UTC, rempas wrote:
>> Exactly! We can mix things up a little! Or even add a new statement 
>> called "match" idk

...

> There’s one more problem: Walter et al. always avoid adding new keywords 
> to the language, preferring to reuse the existing ones whenever 
> possible. Well, we could use `if switch`.

`new switch` ;)