Return false status only when adding a route is failed.  It could
erroneously return false due to an afexists() check loop in routing_start().
vt(4): Change vb_history_size from "int" to "unsigned int"

CID:		1230002, 1230003
MFC after:	1 week
vt(4): Indicate that KDSETRAD case falls through the next case

CID:		1229953
MFC after:	1 week