language: added PreferSameScript MatchOption and added match options. Change-Id: I7c772740515ff557b30fa03be034622b49ea544a Reviewed-on: https://go-review.googlesource.com/47592 Run-TryBot: Marcel van Lohuizen <mpvl@golang.org> Reviewed-by: Nigel Tao <nigeltao@golang.org>