fs/Path: rename to AllocatedPath

The new class Path only holds a string pointer without being
responsible for allocation/deallocation.  The FileSystem.hxx library
accepts Path arguments instead of AllocatedPath, to avoid forcing
callers to allocate another string object.

src/ClientFile.hxx

@@ -35,7 +35,6 @@ class Error;
  * @return true if access is allowed
  */
 bool
-client_allow_file(const Client *client, const Path &path_fs,
-		  Error &error);
+client_allow_file(const Client *client, Path path_fs, Error &error);
 
 #endif