Fix mis-optimization of "expression && non-zero constant" operations with 32-bit type.

The previous code may have been intended to convert this to a "!=0" test, which would have been valid if correctly implemented, but with the current code generator that actually yields worse code than the original version, so for now I just removed the optimization for this case.

This problem could lead to crashes in code like the following (derived from a csmith-generated test case):

#pragma optimize 1
int main(int argc, char *argv[]){
    long l_57 = argc;

    return (4 ^ l_57) && 6;
}

DAG.pas

@@ -1569,9 +1569,7 @@ case op^.opcode of			{check for optimizations of this node}
                      end; {with}
                   opv := op^.right;
                   end; {if}
-               end {if}
-            else
-               op^.opcode := pc_neq;
+               end; {if}
             end; {if}
          end {if}
       else if op^.left^.opcode = pc_ldc then