Reviewed-by: aefimov

Reviewed-by: chegar, jeff, robm

8164480: Crash with assert(handler_address == SharedRuntime::compute_compiled_exc_handler(..) failed: Must be the same
Summary: Exception checking code needs to handle pre-allocated exceptions.
Reviewed-by: thartmann, kvn

Reviewed-by: dholmes, phh

Summary: Improve the nmethod unloading times by optimizing the search for an itable stub in VtableStubs array
Reviewed-by: kvn, coleenp, tschatzl