Fix expression evaluation

The below code wasn't compiling properly:
----8<----
typedef unsigned uint;

int main(void)
{
  uint a;

  a =  0 + sizeof(char[1])*0;
  a = -0 + sizeof(char[1])*0;
/**/  a = +0 + sizeof(char[1])*0; // error: lvalue expected

  labs( 0 + sizeof(char[1])*0);
  labs(-0 + sizeof(char[1])*0);
/**/  labs(+0 + sizeof(char[1])*0); // error: too many function arguments

  printf("%04X\n", (uint)( 0 + sizeof(char[1])*0));
  printf("%04X\n", (uint)(-0 + sizeof(char[1])*0));
  printf("%04X\n", (uint)(+0 + sizeof(char[1])*0)); // error: 1 printed but must be 0

  return 0;
}
----8<----

v0100/smlrc.c

@@ -5720,10 +5720,13 @@ int ParseExpr(int tok, int* GotUnary, int* ExprTypeSynPtr, int* ConstExpr, int*
       if (!j)
       {
         int idx = sp - 1;
+        int outer;
         *ConstVal = exprval(&idx, ExprTypeSynPtr, ConstExpr);
+        outer = idx;
         // remove the unneeded unary +'s that have served their cast-substitute purpose
-        // also remove dereferences of size 0 (dereferences of pointers to structures)
-        for (idx = sp - 1; idx >= 0; idx--)
+        // also remove dereferences of size 0 (dereferences of pointers to structures);
+        // do this only within the current subexpression
+        for (idx = sp - 1; idx > outer; idx--)
           if (stack[idx][0] == tokUnaryPlus ||
               (stack[idx][0] == tokUnaryStar && !stack[idx][1]))
             del(idx, 1);