lua: make luasupp.h self-contained

We need to include "ap_session.h" to define 'struct ap_session'.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

accel-pppd/lua/luasupp.h

@@ -3,6 +3,8 @@
 
 #include <lua.h>
 
+#include "ap_session.h"
+
 int luaopen_lpack(lua_State *L);
 int luaopen_bit(lua_State *L);