hush: fix a bunch of obscure while/until/continue bugs

function                                             old     new   delta
run_list                                            1159    1214     +55
done_pipe                                            106     123     +17
done_command                                          86      98     +12
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 84/0)               Total: 84 bytes

diff --git a/shell/hush_test/hush-misc/continue3.tests b/shell/hush_test/hush-misc/continue3.tests
new file mode 100644
index 0000000..0aff867
--- /dev/null
+++ b/shell/hush_test/hush-misc/continue3.tests
@@ -0,0 +1,3 @@
+# Test that "continue" does affect exitcode (sets to 0)
+e=''
+while echo $?; test $e && exit; true; do e=1; false; continue; done