simplify:

do not set underwater state-bit for submarines when
pos.y + height is still positive (object height can
be changed at runtime and games should not have any
submarine units poking out above the water itfp)

prefer to keep local up-vector as long as possible
add a CMatrix44f SSE test (please can someone with an Intel CPU run it and say if it fails?)
Since all PieceMatrix computations now happen on CPU in our own code, time spend in matrix-matrix multiply increased _a lot_ (in a short test it took 10% cpu usage)
So it makes sense to micro-optimize it (SSE implem. would be 4x faster here)
add NOT_USING_STREFLOP definition option
partly revert "fix clang warnings / duplicate code"
1. when the static const is defined in the .cpp in cannot be inlined
2. you always need to compile float3.cpp (not wanted for UnitTests, tools, ...)
don't compile spring-legacy on "make spring"

target "spring" is only meant to compile the default target
add comment (else it maybe will be reverted again)
fix test_Matrix44f with SIGNAL_NANS & speedup SSE path by another 10%
fix macosx compile
fix #3692
fix #3696 (too much simplification)
fix compile warning: NOT_USING_CREG already defined (via command line)
allow lua ais to be selected with the menu
! LuaUnitDefs: deprecate canHover (check moveDef.family instead)

this tag had no purpose other than to generate a
warning for mobile units that were not hovercraft

GMT: avoid only mobiles, let PFS/CD handle statics
fix #3698 ("merged" games when selecting multiple games & ais in menu)
ProjectileDrawer: setup proper GL state for DrawProjectile
fix part of #3701: made "Player Only: Testing Sandbox" work again
fix clang warning spam
try to fix #3704 (units can jump out of water because of an explosion)
fix #3704
fix #3697

Spring.GetPositionLosState now returns a 4th argument which indicates
if a position is actively being radar- or sonar-jammed by any allyteam