RFC strace via gdbserver

[Stan Cox]

This is a followup to
  https://sourceforge.net/p/strace/mailman/message/34782296/
which describes Josh Stone's work on strace support for the gdb remote 
protocol.
   https://github.com/cuviper/strace/
Initially this effort supported gdbserver "all stop" mechanism, which 
stops all threads.  Support has been added to also support gdbserver 
"non stop" mode; which only stops the examined thread.
  ( info gdb.info 'Non-Stop' )
The non stop protocol uses asynchronous notifications to communicate 
between gdbserver and the client.

Additionally, support for qualifying expressions (-e expr) and following 
children (-f) will be pushed soon.

Also, there is an ongoing effort to allow a gdb client to be examining a 
process via gdbserver while also allowing a remote protocol aware strace 
to attach to the same process via gdbserver.
  ssh://sourceware.org/git/archer.git
  branch scox/strace

Thanks

Stan