This change will only affect rare advanced users that depend on
the return value of `log!` or `event!`. For all other users this
will be a non-breaking change.
Before this commit:
`log!` and `event!` returned true iff signal was allowed.
After this commit:
`log!` and `event!` now ALWAYS return nil.
`log!?` and `event!?` have been added that keep the old behaviour.
Motivation:
It's pretty rare to use the return value when generating log or event
signals. I originally included the return value since it CAN be handy,
and I figured it could just be ignored by those that don't need it.
But #53 showed that there's a downside I hadn't anticipated - some
users may actually depend on / prefer a nil return to prevent
accidentally affecting program flow.
I think that's a legitimate enough concern to still make a change now
before v1 final.
Apologies for the nuissance!
