ash testsuite: add most of hust tests which pass for ash

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash_test/ash-signals/save-ret.tests b/shell/ash_test/ash-signals/save-ret.tests
new file mode 100755
index 0000000..0786b6d
--- /dev/null
+++ b/shell/ash_test/ash-signals/save-ret.tests
@@ -0,0 +1,4 @@
+# make sure we do not corrupt $? across traps
+trap "echo YEAH; false" USR1
+kill -USR1 $$
+echo $?