There seems to be a compatibility problems with Rails +
Rack::Deflater; so we revert this incompatibility.

This effectively reverts r65922; but keeps the bugfixes to
better support non-blocking sockets and pipes for future use.

[Bug #15356] [Bug #14968]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66093 b2dd03c8-39d4-4d8f-98ff-823fe69b080e