Change in Exception re-throwing

Hi, Please take a look into the patch. https://gist.github.com/dstogov/35a480a705b4a96d3d150e4d92dfd1a5 It substitutes calls to zend_throw_exception_internal(NULL) by zend_rethrow_exeption(). This simplifies code and dosn't change any behavior for PHP itself, however this may affect some third-party extensions. Now PHP won't call zend_throw_exception_hook(NULL) and DTRACE_EXCEPTION_THROWN(NULL) multiple times, during stack unwinding. I think these duplicate calls are completely useless. XDEBUG and APM skip hooks with NULL argument, and are not going to be affected by the patch. If nobody object, I'll commit this into PHP master on Monday. Thanks. Dmitry.