on Windows/IIS the function handle_imports not work correctly due to the path separator.

[haoqiren]

the function handle_imports in the file class.add-from-server.php not work correctly on windows,the code below:

if ( $filename !== realpath( $filename ) ) {
continue;
}

on Windows/IIS,the path separator are '\', '$filename !== realpath( $filename )' always is true.