Don't generate a .php wrapper file by default

It's now only generated if something to put in it is specified via:

%pragma(php) include=...

or

%pragma(php) code=...

Examples/test-suite/php/exception_order_runme.php

@@ -1,6 +1,5 @@
 <?
 require "tests.php";
-require "exception_order.php";
 
 check::functions(array('is_python_builtin'));
 check::classes(array('A','E1','E2','E3','exception_order','ET_i','ET_d'));