Updated the status page to reflect the current Linux status.

- Fix for attach by name
- Details for register support
- Punted on i386 details as its status has drifted since this page was originally posted
- Multi-threaded target support is soon to be released on Linux
- Partial back-trace is called out since its a high-profile issue


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@182664 91177308-0d34-0410-b5e6-96231b3b80d8