remove the private hack from CallInst, it was not supposed to hit the branch anyway

as a positive consequence the CallSite::getCallee() methods now can be rewritten to be
a bit more efficient

llvm-svn: 110380
diff --git a/llvm/lib/VMCore/Instructions.cpp b/llvm/lib/VMCore/Instructions.cpp
index e03cc82..9e5fd23 100644
--- a/llvm/lib/VMCore/Instructions.cpp
+++ b/llvm/lib/VMCore/Instructions.cpp
@@ -33,7 +33,7 @@
 User::op_iterator CallSite::getCallee() const {
   Instruction *II(getInstruction());
   return isCall()
-    ? cast</*FIXME: CallInst*/User>(II)->op_end() - 1 // Skip Callee
+    ? cast<CallInst>(II)->op_end() - 1 // Skip Callee
     : cast<InvokeInst>(II)->op_end() - 3; // Skip BB, BB, Callee
 }