Registers a routine to be called at exit time.
The __dllonexit function is analogous to the _onexit function except that the global variables used by that function are not visible to this routine. Instead of global variables, this function uses the pbegin and pend parameters.
The _onexit and atexit functions in a DLL linked with MSVCRT.LIB must maintain their own atexit/_onexit list. This routine is the worker that gets called by such DLLs.
The _PVFV type is defined as typedef void (__cdecl *_PVFV)(void).