hush: fix EXIT trap recursion case; check redirection failures

function                                             old     new   delta                          
run_pipe                                            1299    1328     +29                          
hush_exit                                             90     102     +12                          
hush_main                                           1172    1179      +7                          
run_list                                            1226    1225      -1                          
------------------------------------------------------------------------------                    
(add/remove: 0/0 grow/shrink: 3/1 up/down: 48/-1)              Total: 47 bytes 

diff --git a/shell/hush_test/hush-misc/redir3.right b/shell/hush_test/hush-misc/redir3.right
new file mode 100644
index 0000000..3d20bbf
--- /dev/null
+++ b/shell/hush_test/hush-misc/redir3.right
@@ -0,0 +1,14 @@
+hush: can't open '/does/not/exist': No such file or directory
+One:1
+hush: can't open '/cant/be/created': No such file or directory
+One:1
+Ok
+hush: can't open '/cant/be/created': No such file or directory
+Zero:0
+hush: can't open '/cant/be/created': No such file or directory
+One:1
+hush: can't open '/cant/be/created': No such file or directory
+One:1
+hush: can't open '/cant/be/created': No such file or directory
+Zero:0
+Done