plugins: autoclose: Do autoclose in case the next char is a whitespace

[JoeKar]

For me the current behavior is a bit unexpected too in case the brace is opened before an non white space character and automatically closed. So I'd like to suggest this as the new behavior. Yes, a new option could be introduced instead to control that, but then we end up in too much options.

closes #3133

[JoeKar]

Ok, this significantly changes the behavior, which before would also create a new ()) brace pair before the closing one and previously allowed []). It should be discussed, if we would allow more corner cases.