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_engine.cpp

@@ -32,6 +32,7 @@ extern "C" {
 }
 
 #include "utils.h"
+#include "banned.h"
 
 
 string lua_on_event = "on_event";