r21933c
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Critical fixes:
+ Fixed a weapon firing race condition that could lead to crashes in
networked combat.
+ Fixed the excessive strategic AI tax rate leading to economic
suicide at the start of a game.


Other fixes:
+ It is no longer possible to modify caravan fleets in transition.
+ Fixed an issue that could cause the strategic AI to redesign
constructors and freighters each turn.
+ AI ship designs now consider armor and other available options.
+ Fixed sporadically missing Zuul battle music.