Port the main php_cli_server.inc to use ephemeral ports, thus
allowing CLI server tests to be parallelized.
A complication here is that we also need to give each test a
separate doc root, to avoid index.php files writing over each
other.
Closes GH-6375.
* PHP-5.6:
Handle NULL strings in sapi_cli_server_register_variable().
Allow CLI server test scripts to specify the name of the router file.
Conflicts:
sapi/cli/php_cli_server.c