Enhanced and cleaned up the URL rewriting engine for 1.3:

First the grouped parts of RewriteRule pattern matches (parenthesis!) can be
accessed now via backreferences $1..$9 in RewriteConds test-against strings in
addition to RewriteRules subst string. Second the grouped parts of RewriteCond
pattern matches (parenthesis!) can be accessed now via backreferences %1..%9
both in following RewriteCond test-against strings and RewriteRules subst
string. This provides maximum flexibility through the use of backreferences.
Additionally the rewriting engine was cleaned up by putting common code to the
new expand_backrefs_inbuffer() function.

Submitted by:	Ralf S. Engelschall
Reviewed by:	Dean Gaudet, Ralf S. Engelschall


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@78903 13f79535-47bb-0310-9956-ffa450edef68