Adding a test for full struct tainting

test/constant_time/intraprocedural/struct/tainted_struct_bis.c

+struct foo {
+    int x;
+    int z;
+};
+
+int main(void) {
+    int res = 0;
+    int y = 42;
+    struct foo __attribute__((__taint__)) bar = { y , 50 };
+
+    if (bar.x) // Should be detected
+        res = 42;
+ 
+    if (bar.z) // Should be detected
+        res = 60;   
+
+    return res;
+}