Rewrite ap_unparse_uri_components() to make it safer and more readable.

Submitted by:	"Jeffrey W. Baker" <jwbaker@acm.org>
Reviewed by:	Martin Kraemer, William A. Rowe, Jim Jagielski


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@88351 13f79535-47bb-0310-9956-ffa450edef68