* pinfo.h (winpids::pid_access): New element.

(winpids::winpids): Rejigger to set pinfo_access.
* pinfo.cc (winpids::add): Try to open shared memory region with supplied
pinfo_access first, then default to readonly.
* fhandler_termios.cc (tty_min::kill_pgrp): When getting list of pids to work
with, suggest opening with PID_MAP_RW.
* signal.cc (kill_pgrp): Ditto.
* sigproc.cc (sig_send): Perform a write check on todo prior to attempting to
increment it.  Return EACCES if we can't write to it.

winsup/cygwin/fhandler_termios.cc

@@ -19,6 +19,7 @@ details. */
 #include "sigproc.h"
 #include "pinfo.h"
 #include "tty.h"
+#include "sys/cygwin.h"
 
 /* Common functions shared by tty/console */
 
@@ -84,7 +85,7 @@ void
 tty_min::kill_pgrp (int sig)
 {
   int killself = 0;
-  winpids pids;
+  winpids pids ((DWORD) PID_MAP_RW);
   for (unsigned i = 0; i < pids.npids; i++)
     {
       _pinfo *p = pids[i];