go.image/tiff/lzw: fork the standard library's compress/lzw package.
go.image/tiff/lzw: fork the standard library's compress/lzw package.

This CL has no code changes. Future CLs will modify the code to
implement TIFF's LZW instead of the standard LZW.

LGTM=bradfitz
R=djd, bradfitz
CC=golang-codereviews
https://golang.org/cl/105750044

golang/image