Manpages of src:freeciv in Debian stretch-backports

• freeciv-client(6)
• freeciv-gtk2(6)
• freeciv-gtk3(6)
• freeciv-modpack(6)
• freeciv-mp-gtk3(6)
• freeciv-qt(6)
• freeciv-sdl(6)
• freeciv-sdl2(6)
• freeciv-server(6)
• freeciv(6)