ExceptionHandling Spec: Changed specification for boost::numeric::bad_numeric_cast

* Added B.1.3 and B.1.4 : boost::numeric::bad_numeric_cast and boost::thread_interrupted are not treated
* Removed B.6 (behaviour for bad_numeric_cast)
* Removed C.2.8 (implementation for bad_numeric_cast)
* Re-numbered C.2.9 to C.2.8. It is the last section in C.2 and did not contain any anchors, so no references need to be changed.