message: Minor CMakeLists.txt cleanup
  Instead of hardcoding SOVERSION, use CMake variables to set it up.
  Closes
diff: @@ -53,7 +53,7 @@ if(NOT ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION} STRLESS 3.1 AND ";${CMAKE_C
  target_compile_features(pugixml PUBLIC cxx_long_long_type)
  endif()
  -set_target_properties(pugixml PROPERTIES VERSION ${pugixml_VERSION} SOVERSION 1)
  +set_target_properties(pugixml PROPERTIES VERSION ${PROJECT_VERSION} SOVERSION ${PROJECT_VERSION_MAJOR})
  if(USE_VERSIONED_LIBDIR)
  # Install library into its own directory under LIBDIR
  