Fix printing streampos to ostream

The expression (cout << y) works as described only if no shift operator of streampos into ostream is defined.  That operator may be defined by user code and the result may be different.

Author: yecril71pl

docs/standard-library/ios-typedefs.md

@@ -61,7 +61,7 @@ int main( )
    ofstream x( "iostream.txt" );
    x << "testing";
    streampos y = x.tellp( );
-   cout << y << endl;
+   cout << + y << endl;
 }
 ```