Fix merging of AddDefaultCharset directive.

PR:		5872 (reported against 1.3)
Submitted by:	Jun Kuriyama <kuriyama@imgsrc.co.jp>
Reviewed by:	Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86176 13f79535-47bb-0310-9956-ffa450edef68