lua: fix compilation

Include unistd.h to fix the following error.

----
  CC       liblua_plugin_la-intf.lo
  intf.c: In function 'Start_LuaIntf':
  intf.c:372: error: implicit declaration of function 'close'
----
Signed-off-by: Rafaël Carré <funman@videolan.org>

modules/lua/intf.c

@@ -30,6 +30,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 #include <vlc_common.h>
 #include <vlc_interface.h>