Merge r958253 from trunk:

Stop compressing if we are doing a HEAD request and the content-length filter
can't determine the content-length anyway.

Submitted by: Ruediger Pluem

Submitted by: sf
Reviewed/backported by: jim



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1162858 13f79535-47bb-0310-9956-ffa450edef68