We check for the client Accept-Encoding: "gzip" presence also

We check for the client Accept-Encoding: "gzip" presence also
This should eliminate a lot or reported problems.

Note that this doesn#t fix RSS ssues:
Most RSS clients are NOT(!) application/xml gzip compatible yet.
Even if they are sending the accept-encoding gzip header!
wget is, Mozilla, and MSIE no.
Of the RSS readers only MagpieRSS 0.5.2 is. http://www.rssgov.com/rssparsers.html

git-svn-id: svn://svn.code.sf.net/p/phpwiki/code/trunk@3961 96ab9672-09ca-45d6-a79d-3d69d39ca109