Avoid macros luaL_loadbuffer and luaL_loadfile

Use luaL_loadbufferx and luaL_loadfilex instead, being explicit about
whether to accept binary chunks.

lauxlib.c

@@ -874,7 +874,7 @@ LUALIB_API int luaL_loadbufferx (lua_State *L, const char *buff, size_t size,
 
 
 LUALIB_API int luaL_loadstring (lua_State *L, const char *s) {
-  return luaL_loadbuffer(L, s, strlen(s), s);
+  return luaL_loadbufferx(L, s, strlen(s), s, "t");
 }
 
 /* }====================================================== */