Should guard-foreign-escape use `#:callback-exns?`?

[LiberalArtist]

Now that the #:callback-exns? option for _fun has been added (in https://github.com/racket/racket/commit/bf8741e727fdf1844c65677f9b81ff71e5a42f3d), maybe guard-foreign-escape should use it:

https://github.com/racket/draw/blob/253dbf895966fd8179d4b8c3620c60190647cfd0/draw-lib/racket/draw/unsafe/callback.rkt#L7-L18

[mflatt]

Hm... I thought it was, but that's because I've had the change (uncommitted, as it turns out) in my checkout for months!

I'd be much more comfortable if we had been testing this change for 6 weeks, instead of making it just before a release. So, I'll probably wait until after the release branch before merging.