[IR] Add Instruction::isLifetimeStartOrEnd, NFC

Instruction::isLifetimeStartOrEnd() checks whether an Instruction is an
llvm.lifetime.start or an llvm.lifetime.end intrinsic.

This was suggested as a cleanup in D55967.

Differential Revision: https://reviews.llvm.org/D56019

llvm-svn: 349964
diff --git a/llvm/lib/Transforms/Utils/Evaluator.cpp b/llvm/lib/Transforms/Utils/Evaluator.cpp
index 992c8b9..e875cd6 100644
--- a/llvm/lib/Transforms/Utils/Evaluator.cpp
+++ b/llvm/lib/Transforms/Utils/Evaluator.cpp
@@ -483,8 +483,7 @@
           }
         }
 
-        if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
-            II->getIntrinsicID() == Intrinsic::lifetime_end) {
+        if (II->isLifetimeStartOrEnd()) {
           LLVM_DEBUG(dbgs() << "Ignoring lifetime intrinsic.\n");
           ++CurInst;
           continue;