ruby: test for DeadStore and captured variables

ruby/ql/test/query-tests/variables/DeadStoreOfLocal/DeadStoreOfLocal.expected

@@ -1 +1,2 @@
 | DeadStoreOfLocal.rb:2:5:2:5 | y | This assignment to $@ is useless, since its value is never read. | DeadStoreOfLocal.rb:2:5:2:5 | y | y |
+| DeadStoreOfLocal.rb:61:17:61:17 | x | This assignment to $@ is useless, since its value is never read. | DeadStoreOfLocal.rb:56:17:56:17 | x | x |

ruby/ql/test/query-tests/variables/DeadStoreOfLocal/DeadStoreOfLocal.rb

@@ -33,4 +33,34 @@ class Sub < Sup
         y = 3  # OK - the call to `super` sees the value of `y``
         super
     end
+end
+
+def do_twice
+    yield
+    yield
+end
+    
+def get_done_twice x
+    do_twice do
+        print x
+        x += 1  # OK - the block is executed twice
+    end
+end
+
+def retry_once
+    yield
+rescue
+    yield
+end
+    
+def get_retried x
+    retry_once do
+        print x
+        if x < 1
+            begin
+                x += 1  #$ SPURIOUS: Alert
+                raise StandardError
+            end
+        end
+    end
 end