* doc/tar.texi (gzip): Don't claim that -I 'gzip --best' works.
Problem reported by Davide Brini in
<http://lists.gnu.org/archive/html/bug-tar/2012-07/msg00025.html>.
Also, improve some of the surrounding text.
This file is a placeholder. It will be replaced with the actual ChangeLog
by make dist. Run make ChangeLog if you wish to create it earlier.