Update of the release notes to provide examples of the new checks/warnings

git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_34@197667 91177308-0d34-0410-b5e6-96231b3b80d8
Remove help notes from the ReleaseNotes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_34@197841 91177308-0d34-0410-b5e6-96231b3b80d8