* cygthread.cc (cygthread::stub): Detect if thread function wants to release

itself here, to avoid a race.
(cygthread::release): Clear more stuff.  Add a diagnostic for an internal
error.
* cygthread.h (auto_release): New function.
* pinfo.h (pinfo::remember): Add an argument to denote whether child is
detached.
* fork.cc (fork_parent): Reflect change in arguments to pinfo::remember.
* pinfo.cc (_pinfo::exit): Signal exit more forcibly.
(proc_waiter): Use cygthread::auto_release to signify that cygthread::stub
should release the thread.  This should avoid a race.
(pinfo::alert_parent): Don't signify an error when wr_proc_pipe == NULL.
* sigproc.cc (proc_subproc): Add support for PROC_DETACHED_CHILD.
* sigproc.h: Ditto.
* spawn.cc (spawn_guts): Specify whether child is detached or not when calling
pinfo::remember.

winsup/cygwin/sigproc.h

@@ -30,11 +30,11 @@ enum
 
 enum procstuff
 {
-  PROC_ADDCHILD		= 1,	// add a new subprocess to list
-  PROC_CHILDTERMINATED	= 2,	// a child died
-  PROC_CLEARWAIT	= 3,	// clear all waits - signal arrived
-  PROC_WAIT		= 4,	// setup for wait() for subproc
-  PROC_NOTHING		= 5	// nothing, really
+  PROC_ADDCHILD		  = 1,	// add a new subprocess to list
+  PROC_DETACHED_CHILD	  = 2,	// set up a detached child
+  PROC_CLEARWAIT	  = 3,	// clear all waits - signal arrived
+  PROC_WAIT		  = 4,	// setup for wait() for subproc
+  PROC_NOTHING		  = 5	// nothing, really
 };
 
 struct sigpacket