stand: lua: break out a few more dirent types in lfs

These are non-standard and specific to the version used in loader.  We
have some desire to recognize symlinks to avoid filtering out kernel
symlinks in the autodetection bits when they would be perfectly fine to
`load`.

This won't be usable right away, so any impending use will need to be
careful to account for nil.

Reported by:	leres

libexec/flua/lfs/lfs.c

@@ -444,6 +444,10 @@ luaopen_lfs(lua_State *L)
 	/* Non-standard extension for loader, used with lfs.dir(). */
 	lua_pushinteger(L, DT_DIR);
 	lua_setfield(L, -2, "DT_DIR");
+	lua_pushinteger(L, DT_REG);
+	lua_setfield(L, -2, "DT_REG");
+	lua_pushinteger(L, DT_LNK);
+	lua_setfield(L, -2, "DT_LNK");
 #endif
 	return 1;
 }