Fix the bug demonstrated by the previous commit:
take_casualties_from_lands() limits total casualties to @each. It
should limit each land unit's casualties, and only if !may_kill. This
can lead to fewer casualties than called for; oops in
take_casualties(). Broken in commit 025e9cc25, v4.4.0.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>