Since 4623c603 the assertions in
lcl_IsLessStart/lcl_IsLessEnd trigger spuriously, because the comparison
is invoked always now even on identical pointers, while the SvArray only
invoked it if the 2 hints didn't have the same address; move the
assertion to SwpHintsArray::Check().

Change-Id: Ida6c8e268452343ed3e90410636703c6baffbabd