Add routing front/back ends

This adds a URL mapping library that can be used to implement virtual
paths. Also, "web/html/index.php" is moved to "web/html/home.php" and
"web/html/index.php" becomes a routing front end that maps virtual paths
to corresponding files.

To enable the virtual path feature, all requests need to be redirected
to the "index.php" routing script. If you use lighttpd, following
rewrite rule can be used:

    url.rewrite = ( "^(.*)$" => "/index.php/$1" )

A similar rule can be used for Apache (using mod_rewrite).

Note that the current routing front end only works if PATH_INFO is
provided.

Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>

web/lib/config.inc.php.proto

@@ -51,3 +51,7 @@ $DISABLE_HTTP_LOGIN = true;
 
 # Web URL used in email links and absolute redirects, no trailing slash
 $AUR_LOCATION = "http://localhost";
+
+# Use virtual URLs -- to enable this feature, you also need to tell your web
+# server to redirect all requests to "/index.php/$uri".
+$USE_VIRTUAL_URLS = true;