Add patches to show the result at the end of each bench

Signed-off-by: Alban Gruin <alban.gruin@irit.fr>

bench/return.cocci

+@@
+expression A;
+@@
+
+int main(...)
+{
++ int res;
+...
+
+- return A;
++ res = A;
++ print_int(res);
++ return res;
+}