Give Int an initializer that takes a single Character

[Nevin]

@lancep

I’ll admit, I don’t hit this a lot. But it is one of those things where it seems silly to have to make a heap allocation for a String to just parse out the Int from a Character you already have.

Once we get short-string optimizations as discussed in this thread (similar to NSString tagged-pointers) then there won’t be any heap allocation for this scenario. Hopefully that should land by Swift 5.