feat(lua): Port of NodeMCU Lua53 read-only tables (#2994)

* chore(lua): revert useless c light function change

This change was part of the eLua LTR patches (based on 5.1), whereby this feature was already integrated in Lua 5.2.

* feat(lua): port of NodeMCU Lua53 read-only tables

# Conflicts:
#	radio/src/lua/CMakeLists.txt
#	radio/src/lua/api_general.cpp

* fix(nv14): missing SDRAM definition

* fix: l_mathop

* fix: use float functions in drawPower()

* fix: ltable resize

* fix: correct name is "bit32"

* fix: first Lua context must be closed last

As the lookup cache is attached to that one

* Revert to Lua using double

* Ensure byte-code compatibility

* Fix possible compatibility issue with `lua_typename`/`luaL_typename`

* Fix Bitmap symbol table

* Re-add table lib for COLORLCD

radio/src/lua/api_filesystem.cpp

@@ -19,10 +19,11 @@
  * GNU General Public License for more details.
  */
 
+#define LUA_LIB
 
 #include <cstdio>
-#include "lua_api.h"
 
+#include "lua_api.h"
 #include "api_filesystem.h"
 
 // garbage collector for luaDir
@@ -33,18 +34,6 @@ static int dir_gc(lua_State* L)
   return 0;
 }
 
-void registerDirIter(lua_State* L)
-{
-  luaL_newmetatable(L, DIR_METATABLE);
-  
-  /* set the garbage colector field */
-  lua_pushstring(L, "__gc");
-  lua_pushcfunction(L, dir_gc);
-  lua_settable(L, -3);
-
-  lua_pop(L, 1);
-}
-
 static int dir_iter(lua_State* L)
 {
   DIR* dir = (DIR*)lua_touserdata(L, lua_upvalueindex(1));
@@ -160,4 +149,21 @@ int luaFstat(lua_State* L)
   lua_settable(L, -3);
 
   return 1;
-}
+}
+
+
+LROT_BEGIN(dir_handle, NULL, LROT_MASK_GC)
+  LROT_FUNCENTRY( __gc, dir_gc )
+LROT_END(dir_handle, NULL, LROT_MASK_GC)
+
+LROT_BEGIN(etxdir, NULL, 0)
+  LROT_FUNCENTRY( dir, luaDir )
+  LROT_FUNCENTRY( fstat, luaFstat )
+LROT_END(etxdir, NULL, 0)
+
+extern "C" {
+  LUAMOD_API int luaopen_etxdir(lua_State* L) {
+    luaL_rometatable( L, DIR_METATABLE,  LROT_TABLEREF(dir_handle));
+    return 0;
+  }
+}