Revert r181833: lldb prompt issue still occurs on buildbot (http://lab.llvm.org:8011/builders/lldb-x86_64-linux/builds/4124)
- maybe consider checking in the 'good' version of libedit to avoid ancient system version



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@181903 91177308-0d34-0410-b5e6-96231b3b80d8