msh: create testsuite (based on hush one)
hush: add TODO (doesn't know ":" command)

diff --git a/shell/hush_test/zbad b/shell/hush_test/zbad
new file mode 100644
index 0000000..e4b5caa
--- /dev/null
+++ b/shell/hush_test/zbad
@@ -0,0 +1,3 @@
+# TODO: hush doesn't know ':' null command
+
+while :; do exit; done