ash: copy three tests from hush_test/hush-signals/*

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash_test/ash-signals/catch.tests b/shell/ash_test/ash-signals/catch.tests
new file mode 100755
index 0000000..d2a21d1
--- /dev/null
+++ b/shell/ash_test/ash-signals/catch.tests
@@ -0,0 +1,20 @@
+# avoid ugly warnings about signals not being caught
+trap ":" USR1 USR2
+
+"$THIS_SH" -c '
+trap "echo caught" USR2
+echo "sending USR2"
+kill -USR2 $$
+
+trap "" USR2
+echo "sending USR2"
+kill -USR2 $$
+
+trap "-" USR2
+echo "sending USR2"
+kill -USR2 $$
+
+echo "not reached"
+'
+
+trap "-" USR1 USR2