Follow up to r1879079: merge slashes (if configured to) before pre_trans

There are few cases (if any) where multiple slashes have different semantics
than a single one, and it's always been like that for proxy_trans anyway.

This allows for better directory/location/if walk caching and is less confusing
for their users.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1879117 13f79535-47bb-0310-9956-ffa450edef68
