Add new FileCheck feature to 3.4 release notes

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194456 91177308-0d34-0410-b5e6-96231b3b80d8
Correct a glitch in r194424 which may invalidate iterator.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194457 91177308-0d34-0410-b5e6-96231b3b80d8