attack assault paradrop: Don't disclose defender's retreats

attack assault paradrop: Don't disclose defender's retreats

When an attacking land unit fails its morale check and retreats, the
retreat message needs to be prefixed with a newline to separate it
from the casualty characters.  However, the code also prints the
newline when a defending land unit retreats, leaking the retreat to
the attacker.  For instance, a fight that forces three defending to
retreat could look like this:

    !!!!!!!!!!!!!!!!!!
    !@!!!!!!!!!!!!!@!
    !

    - Casualties -
	 Yours: 2
	Theirs: 34

Messed up in Empire 3.  Fix by printing the newline only when an
attacking land unit retreats.  The example becomes:

    !!!!!!!!!!!!!!!!!!!@!!!!!!!!!!!!!@!!
    - Casualties -
	 Yours: 2
	Theirs: 34

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>