Increase the gdb-remote packet timeout for the first packet we send
to the remote side (QStartNoAckMode) - it may take a little longer
than normal to get a reply.

In debugserver, hardcode the priority for several threads so they
aren't de-prioritized when a user app is using system resources.
Also, set the names of the threads.

<rdar://problem/17509866>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@213828 91177308-0d34-0410-b5e6-96231b3b80d8