feat(userspace): Add banned.h which includes banned functions.

This defines certain functions as invalid tokens, i.e., when
compiled, the compiler throws an error.

Currently only `strcpy` is included as a banned function.

Fixes #788

Signed-off-by: Vaibhav <vrongmeal@gmail.com>

userspace/engine/falco_utils.cpp

@@ -18,6 +18,7 @@ limitations under the License.
 */
 
 #include "falco_utils.h"
+#include "banned.h"
 
 namespace falco
 {