[Freeciv-Dev] (PR#4692) F3 players menu needs scrolling

["Guest" <rt-guest@xxxxxxxxxxxxxx>]

When there are a large number of players, the players menu extends below
the bottom of the screen and its buttons cannot be seen or pressed. This
occurs in version 1.14.0 gui-gtk on Suse 8.0, and makes multiplayer
games difficult when players cannot remember the menu's hotkeys (cLose
Intel Meet Canceltreaty Withdrawvision Spaceship).

Suggested way to fix: Have a default max menu height, say 30 players,
above which the menu does not grow and is scrolled. If a player resizes
the window up or down, this becomes the new default saved in their
settings on the window's close.

By the way, aifill 100 + barb 4 on the Europe map rocks.