LOS/FOV code fixes & speed updates

Talents bound to "left- and middle-click on target" no longer work on unseen (i.e., invisible) actors.
Location of unseen (i.e., invisible) actors may not be inferred from targeting highlights.
Targeting highlights now show how a targeting path is blocked when blocked by a corner of an adjacent obstructed tile.


git-svn-id: http://svn.net-core.org/repos/t-engine4@4590 51575b47-30f0-44d4-a5cc-537603b46e54