API CanSummonFriend

__NOTOC__
Returns whether you can RaF summon a particular unit.
 summonable = CanSummonFriend(unit)
==Arguments==
:;unit: : UnitId - The player to check whether you can summon.
==Returns==
:;summonable: - 1 if you can summon the unit using RaF, nil otherwise.
==Example==
The snippet below checks whether you can summon the target, and, if so, whispers and summons her to you.
 local t = "target"; 
 if CanSummonFriend(t) then 
 SendChatMessage("I am summoning you!","WHISPER",nil,t) 
 SummonFriend(t) 
 end