fix LoS

 - when a calculation is made to a potentially spotted enemy unit,
   but another unit is blocking that LoS, the trajectory stops at
   that unit and TileEngine::visible() returns true.
 - this fix includes a last check to ensure that the unit that's
   attempting to be spotted is really the unit that the trajectory
   stops at. If not, return false.
bigger bases have bigger detection chance...
Merge pull request #2 from SupSuper/master

synchro
Update Zoom.cpp
Merge pull request #676 from GixG/compilWarning

Fix bug #295
Merge pull request #661 from kevL/visible_fix

fix LoS
Merge pull request #665 from kevL/detect_xbase_fix

bigger bases have bigger detection chance...