ash,hush: add a test that "continue" does not cripple traps

Both shells pass this test.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash_test/ash-signals/continue_and_trap1.right

@@ -0,0 +1 @@
+Exiting

shell/ash_test/ash-signals/continue_and_trap1.tests

@@ -0,0 +1,7 @@
+trap "echo Exiting; exit" INT
+
+(sleep 1; kill -s INT $$) &
+
+while continue; do
+        continue;
+done

shell/hush_test/hush-signals/continue_and_trap1.right

@@ -0,0 +1 @@
+Exiting

shell/hush_test/hush-signals/continue_and_trap1.tests

@@ -0,0 +1,7 @@
+trap "echo Exiting; exit" INT
+
+(sleep 1; kill -s INT $$) &
+
+while continue; do
+        continue;
+done