[PATCH] Executor improvements

Hi, The proposed patch for PHP improves the executor. At first it eliminates direct execute() recursion so the following script won't produce SIGSEGV anymore (It'll produce memory overflow error instead). <?php function foo() { foo(); } foo(); ?> Note that in case some extension (e.q. xdebug) override zend_execute(), VM will use recursive calls. At second executor now uses "fastcall" calling convention, and as result it gives ~5% speedup on bench.php (~3.8 sec instead of ~4.0 sec) Any objections? Thanks. Dmitry.