[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349964 91177308-0d34-0410-b5e6-96231b3b80d8
18 files changed