Update Release Notes for 3.4.1

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_34@208596 91177308-0d34-0410-b5e6-96231b3b80d8
Bump version to 3.4.2

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_34@208597 91177308-0d34-0410-b5e6-96231b3b80d8