Merge tag 'upstream/1.6'

Upstream version 1.6

Conflicts:
	gzip.1
	gzip.c
	zdiff.1

diff --cc deflate.c
Simple merge

diff --cc doc/gzip.texi
Simple merge

diff --cc gzip.c
Simple merge

diff --cc gzip.h
Simple merge

diff --cc zdiff.1
Simple merge