Point defense DF weapons, max engines in XL fgtrs

[douglas]

The problem with targetting seekers in tactical combat is a UI issue that is not likely to ever get fixed. Most people around here don't care particularly much because the mods that use such weapons are primarily meant for multiplayer, with pretty much no work done on AI at all, where tactical combat just doesn't matter.

The bug with speed dropping to 0 on the fighters is because the number of standard movement points a design has (which is divided by the hull's engines per move setting to get actual speed) is stored in a single byte. It wraps around to 0 when it would go past 255.