* exceptions.cc (interruptible): Change method for determining if something is

interruptible.
(call_handler): Avoid suspending a thread if it owns a mutex.  Only set
signal_arrived if the thread was actually interrupted.
(events_init): Initialize module information needed by interruptible().
(sigdelayed): Don't call sig_dispatch_pending since it could screw up
* init.cc (dll_entry): Record module handle of main for use by interruptible().
(proc_subproc): Reorganize handling of terminated child so that the bulk of the
processing comes from the signal thread.
(wait_sig): Force processing of waiting threads if SIGCHLD is not processed.
* sync.cc (muto::release): Set tid == 0 after lock is released or signal
processor will be confused.

winsup/cygwin/sigproc.h

@@ -18,7 +18,8 @@ enum procstuff
   PROC_CHILDSTOPPED	= 2,	// a child stopped
   PROC_CHILDTERMINATED	= 3,	// a child died
   PROC_CLEARWAIT	= 4,	// clear all waits - signal arrived
-  PROC_WAIT		= 5	// setup for wait() for subproc
+  PROC_WAIT		= 5,	// setup for wait() for subproc
+  PROC_SIGCHLD		= 6	// saw a non-trapped SIGCHLD
 };
 
 typedef struct struct_waitq