Handle non-semantic nodes preceding the bound form of quote, unquote, etc

[cespare]

For example

@ ; surprisingly,
; this is a valid deref.
x

This happens with derefs, quotes, unquotes, unquote splices, syntax quotes, metadata, and the 'ignore next form' dispatch macro.

Right now the intermediate non-semantic nodes (comments, newlines) interfere if we're using ignoreNonSemantic: false.

This isn't something a human would probably write but we need to handle it anyway.

Open question: where should the non-semantic nodes be bound? (Maybe just put them after the form.)