Wrong useless parenthesis elision

@victor found a severe bug in parenthesis elision. The use case is the following

cout  << " - 2 + 3  = "<< - 2 + 3 << "\n";
cout  << "(- 2 + 3) = "<< (- 2 + 3) << "\n";

while these two piece of code should produce the same result, one gets the following output

 - 2 + 3  = 1
(- 2 + 3) = -2