Bump version, as it changes the public API.

CMakeLists.txt

 # SPDX-License-Identifier: CC0-1.0
 # SPDX-FileCopyrightText: none
 cmake_minimum_required(VERSION 3.16 FATAL_ERROR)
-set(PIM_VERSION "5.21.42")
+set(PIM_VERSION "5.21.43")
 
 
 project(Messagelib VERSION ${PIM_VERSION})