  This paper has been withdrawn by the authors. We performed additional
zero-field muon spin relaxation measurements in the superconducting state of
CeIrIn$_5$ and found that the spontaneous fields reported previously below
$T_c$ are not present. Thus, there is no evidence for a
time-reversal-symmetry-violating superconducting order parameter. These new
zero-field measurements, as well as new measurements of the penetration depth
in this system, will be reported elsewhere. Our zero-field measurements in
CeIr$_{0.5}$Rh$_{0.5}$In$_5$, reporting coexistence of superconductivity and
magnetic order, are still valid.
