PR#94: Content negot fails unless each varient has a charset

This was applied to 1.2.1 but missed in 1.3.  We also include here a
later update from Paul.

Reviewed by:	Dean Gaudet, Alexei Kosut, Randy Terbush
Submitted by:	Paul Sutton


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@78662 13f79535-47bb-0310-9956-ffa450edef68