Needs to be updated according to January tc39 mtg consensus

[Mark S. Miller]

As recorded at https://esdiscuss.org/notes/2016-01/2016-01-28.md

Keep exactly the original source text starting from the position of the first token of the production and ending at the position of the last token. Within this text, keep comments and newlines. Still no conclusion about insignificant whitespace, i.e., whitespace other than newlines.

This should significantly reduce the case enumeration in the proposal, as well as being more useful for mobile code.