Add VALIDATE_LUA as a function in lpxserver and lpxclient

luprex/cpp/core/luastack.hpp

@@ -792,6 +792,19 @@ public:
     //
     bool next(LuaSlot tab, LuaSlot key, LuaSlot val) const;
 
+    // Compile lua code.
+    //
+    // If the code contains a syntax error, then the result variable
+    // is set to the error message, and the error message is returned.
+    //
+    // If the code is valid, then the result variable is set to a
+    // closure, and an empty string is returned.
+    //
+    // If a syntax error occurs, the error message may contain the
+    // token <eof>.  If so, the problem is an incomplete expression.
+    //
+    eng::string load(LuaSlot result, std::string_view code, std::string_view context);
+
     // Return true if the int64 can be stored losslessly in a lua_Number.
     //
     // Lua numbers are actually double-precision floating point.  double