Bug fixes:
----------

- Revamp signals so that signals-to-threads more closely mimic Linux
  operation.
  First step of fix for: http://cygwin.com/ml/cygwin/2012-05/msg00186.html
  as well as observed Linux behavior.

- Revert to only creating a new session leader when we know that a
  console process is started in the background.
  Should fix: http://cygwin.com/ml/cygwin/2012-08/threads.html#00062

- Fix mysterious crashes when accessing /etc.
  Fixes: http://cygwin.com/ml/cygwin/2012-07/threads.html#00613 and others.

- Fix a potential race condition starting multiple "first" Cygwin processes
  concurrently.
  Should fix: http://cygwin.com/ml/cygwin/2012-07/msg00531.html

- Fix a bug in unlink/rmdir which could result in removing non-empty
  directories on network drives.  Also fix problems trying to rename files
  under newer Samba versions.
  Fixes: http://cygwin.com/ml/cygwin/2012-07/threads.html#00477

- Prefer to call WSARecvMsg from recvmsg if possible.
  Fixes: http://cygwin.com/ml/cygwin/2012-07/msg00662.html