Ajout de deux programmes sur les stringstreams

test~coding~readingCppPrograms.fr/data/file_istringstream.cpp

+#include <iostream>
+#include <sstream>
+using namespace std;
+
+int main() {
+    string s = "12 1 4 5";
+    istringstream a(s);
+    int i, j, k;
+
+    a >> i >> j >> k;
+
+    cout << k << endl;
+    return 0;
+}

test~coding~readingCppPrograms.fr/data/file_ostringstream.cpp

+#include <iostream>
+#include <sstream>
+using namespace std;
+
+int main() {
+    ostringstream flux;
+
+    flux << "41+1=" << 41+1;
+    string s = flux.str();
+
+    cout << s.length() << endl;
+    return 0;
+}