* fork.cc (fork_parent): Reinstate "childhProc" protection. Don't close

hProcess handle here since it is used to ensure that a new process isn't
created with the old pid after the old pid exits.
* spawn.cc (spawn_guts): Ditto.
* pinfo.cc (proc_waiter): Don't send any signals if we've execed since this
process doesn't officially exist.
* pinfo.h (pinfo::pid_handle): Eliminate.  Just use hProc.
* sigproc.cc (sig_send): Don't send any signals if our sendsig doesn't exist.
That's a sign that we are execing.
(remove_proc): Eliminate pid_handle close.

winsup/cygwin/spawn.cc

@@ -784,7 +784,7 @@ spawn_guts (const char * prog_arg, const char *const *argv,
 		  rc ? cygpid : (unsigned int) -1, prog_arg, one_line.buf);
 
   /* Name the handle similarly to proc_subproc. */
-  ProtectHandle (pi.hProcess);
+  ProtectHandle1 (pi.hProcess, childhProc);
 
   bool wait_for_myself = false;
   if (mode == _P_OVERLAY)
@@ -802,7 +802,6 @@ spawn_guts (const char * prog_arg, const char *const *argv,
 	this). */
       if (!myself->wr_proc_pipe)
        {
-	 myself.hProcess = pi.hProcess;
 	 myself.remember ();
 	 wait_for_myself = true;
 	 myself->wr_proc_pipe = INVALID_HANDLE_VALUE;
@@ -855,8 +854,6 @@ if (wait_for_myself)
 else
   ciresrv.sync (myself, INFINITE);
 
-ForceCloseHandle (pi.hProcess);
-
 switch (mode)
   {
   case _P_OVERLAY: