Proper URI-encoding in InternalServer::build_redirect()

- Before this change `InternalServer::build_redirect()` only URI-encoded the
  article path, ignoring the book name and/or the root location components of
  the URL.

- In order to be able to test this fix, corner_cases.zim was renamed to
  contain a couple of special URL symbols in its filename. The
  `create_corner_cases_zim_file` script was updated accordingly.

test/server_search.cpp

@@ -1517,7 +1517,7 @@ TEST(ServerSearchTest, searchInMultilanguageBookSetIsDenied)
   const ZimFileServer::FilePathCollection ZIMFILES{
     "./test/zimfile.zim",       // eng
     "./test/example.zim",       // en
-    "./test/corner_cases.zim"   // =en
+    "./test/corner_cases#&.zim" // =en
   };
 
   ZimFileServer zfs(SERVER_PORT, ZimFileServer::DEFAULT_OPTIONS, ZIMFILES);