CLuaInstVideo: Add getNeutrinoMode()

- Set Lua api version to 1.28

Example:
	video = video.new()
	if video.getNeutrinoMode() == NMODE.TS then
		messagebox.exec{title="Attention!", text="Movie player is busy.", buttons={ "ok" } }
	end

src/gui/lua/luainstance.h

@@ -31,7 +31,7 @@ extern "C" {
 #include "luainstance_helpers.h"
 
 #define LUA_API_VERSION_MAJOR 1
-#define LUA_API_VERSION_MINOR 27
+#define LUA_API_VERSION_MINOR 28
 
 /* inspired by Steve Kemp http://www.steve.org.uk/ */
 class CLuaInstance