Streamline the AddDefaultCharset directive. Now this one directive

controls the entire 'charset' specification setup. If there is
heartburn, I have no trouble with backing this out, but it makes
live easier for those not using the "default" charset, and reduces
directive bloat a bit :)

PR:
Obtained from:
Submitted by:
Reviewed by:	Martin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@84564 13f79535-47bb-0310-9956-ffa450edef68