Fix several register allocation issues revealed by fuzzer:

test/mjsunit/fuzz-natives.js

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-// Flags: --allow-natives-syntax --noalways-opt
+// Flags: --allow-natives-syntax
 
 var RUN_WITH_ALL_ARGUMENT_ENTRIES = false;
 var kOnManyArgumentsRemove = 5;
 
 function makeArguments() {
   var result = [ ];
   result.push(17);
   result.push(-31);
   result.push(new Array(100));
   result.push(new Array(100003));
@@ skipping 159 matching lines @@
     if (name in knownProblems || name in currentlyUncallable)
       continue;
     print(name);
     var argc = nativeInfo[1];
     testArgumentCount(name, argc);
     testArgumentTypes(name, argc);
   }
 }
 
 testNatives();