fix ltui.lcurses export func name on windows

src/core/lcurses/lcurses.c

@@ -2331,6 +2331,10 @@ static const luaL_Reg curseslib[] =
     {NULL, NULL}
 };
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 __export int luaopen_ltui_lcurses (lua_State *L)
 {
     /*
@@ -2383,6 +2387,10 @@ __export int luaopen_ltui_lcurses (lua_State *L)
     return 1;
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 /* initialize the character map table with the known values after
 ** curses initialization (for ACS_xxx values) */
 static void init_ascii_map()