update to build the version 2.4.2 of freeciv and build sdl & gtk3 client

update to build the version 2.4.2 of freeciv 
build by default the sdl and gtk3 client
      ( inspired Elmo Todurov by https://github.com/cizra/homebrew-games/commit/8e6b5a999d9a4586fb8e3ea74bedd4a2046ff024 )