o Add SIM_SIGFPE to sim-signals

o Start SIM_SIG* at 64 so that the use of host signal numbers can be
  detected and reported.
o Update MIPS simulator to use sim-signal.

sim/common/sim-signal.c

@@ -70,6 +70,12 @@ sim_signal_to_host (SIM_DESC sd, SIM_SIGNAL sig)
     case SIM_SIGXCPU :
 #ifdef SIGXCPU
       return SIGXCPU;
+#endif
+      break;
+
+    case SIM_SIGFPE:
+#ifdef SIGXCPU
+      return SIGFPE;
 #endif
       break;
     }