added basic tests for while/until/break/next

test/t/iterations.rb

+assert('while expression', '11.5.2.3.2') do
+  idx = 10
+  all = []
+  res = while idx > 0
+    all << idx
+    idx -= 1
+  end
+
+  assert_equal nil, res
+  assert_equal [10,9,8,7,6,5,4,3,2,1], all
+end
+
+assert('until expression', '11.5.2.3.3') do
+  idx = 10
+  all = []
+  res = until idx == 0
+    all << idx
+    idx -= 1
+  end
+
+  assert_equal nil, res
+  assert_equal [10,9,8,7,6,5,4,3,2,1], all
+end
+
+assert('break expression', '11.5.2.4.3') do
+  assert_equal :result do
+    while true
+      break :result
+    end
+  end
+
+  assert_equal :result do
+    until false
+      break :result
+    end
+  end
+end
+
+assert('next expression', '11.5.2.4.4') do
+  assert_equal [8,6,4,2,0] do
+    all = []
+    idx = 10
+    while idx > 0
+      idx -= 1
+      next if (idx % 2) == 1
+      all << idx
+    end
+    all
+  end
+
+  assert_equal [8,6,4,2,0] do
+    all = []
+    idx = 10
+    until idx == 0
+      idx -= 1
+      next if (idx % 2) == 1
+      all << idx
+    end
+    all
+  end
+end
\ No newline at end of file