tiff/lzw: sync with the stdlib compress/lzw.

As noted at the top of reader.go, this package is a fork of the standard
library's LZW package, due to an "off by one" in the TIFF format. Grep
for "NOTE" in the Go code for more details.

This commit picks up an upstream change:
https://go-review.googlesource.com/14410 "tidy up some flush calls"

Picking up the more recent change:
https://go-review.googlesource.com/42032 "fix hi code overflow"
will be a follow-up commit, separate from this straightforward commit,
since it has a non-trivial interaction with that off by one.

Change-Id: Iaf795d11590b3e3e0891e3ea3f04b696de4243c9
Reviewed-on: https://go-review.googlesource.com/42191
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
1 file changed