add struct example

examples/c/struct4.c

@@ -0,0 +1,19 @@
+int nonce = 1; // For random input
+
+struct Foo
+{
+    int x;
+};
+
+struct Foo f()
+{
+    struct Foo x;
+    x.x = nonce;
+    return x;
+}
+
+int main()
+{
+    int x = f().x;
+    return x;
+}