Remove threshold for lifetime marker insertion of named temporaries

Now that TailRecursionElimination has been fixed with r222354, the
threshold on size for lifetime marker insertion can be removed. This
only affects named temporary though, as the patch for unnamed temporaries
is still in progress.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@222993 91177308-0d34-0410-b5e6-96231b3b80d8