Change SOversion to 4.2.0 instead of 5.0.0

CMakeLists.txt

@@ -19,8 +19,8 @@ set(APPLICATION_VERSION "${APPLICATION_VERSION_MAJOR}.${APPLICATION_VERSION_MINO
 #     Increment AGE. Set REVISION to 0
 #   If the source code was changed, but there were no interface changes:
 #     Increment REVISION.
-set(LIBRARY_VERSION "5.0.0")
-set(LIBRARY_SOVERSION "5")
+set(LIBRARY_VERSION "4.2.0")
+set(LIBRARY_SOVERSION "4")
 
 # where to look first for cmake modules, before ${CMAKE_ROOT}/Modules/ is checked
 set(CMAKE_MODULE_PATH