* select.cc (thread_pipe): Add paranoid check to ensure thread termination.

* select.cc (thread_pipe): Add paranoid check to ensure thread termination.
* external.cc: Eliminate obsolete include.
* getopt.c (getopt_long): Fix compiler warning.
* shared.h: Moved PID_ definitions to include/sys/cygwin so that they can be
used by external programs.
* include/sys/cygwin.h: Move external definitions here.  Include sys/resource.h
to avoid having to do this everywhere.