player_death strace fix-up

This should be a better fix for this old error.  Check attacker/hidden are in game/connected
using Client_IsIngame smlib stock.

L 01/13/2013 - 21:33:36: [SM] Native "GetClientUserId" reported: Client index 0 is invalid
L 01/13/2013 - 21:33:36: [SM] Displaying call stack trace for plugin "hidden.smx":
L 01/13/2013 - 21:33:36: [SM]   [0]  Line 426, hidden.sp::player_death()
Add public cvar for plugin tracking

* public cvar == sm_tf2hidden_version
* removed compile build script, so it does not end up in archive