BUILD/MINOR: lua: ensure that hlua_ctx_destroy is properly defined

When Lua is disabled, the alternate functions must have the same
prototype as the original ones, otherwise we get such warnings :

src/stream.c:278:27: warning: too many arguments in call to 'hlua_ctx_destroy'
        hlua_ctx_destroy(&s->hlua);
        ~~~~~~~~~~~~~~~~         ^
No backport is needed.

include/proto/hlua.h

@@ -37,7 +37,7 @@ int hlua_post_init();
 /* Empty function for compilation without Lua. */
 static inline void hlua_init() { }
 static inline int hlua_post_init() { return 1; }
-static inline void hlua_ctx_destroy() { }
+static inline void hlua_ctx_destroy(struct hlua *lua) { }
 
 #endif /* USE_LUA */