Add IPv6#link_local?

lib/ipaddress/ipv6.rb

@@ -397,6 +397,13 @@ module IPAddress;
       @compressed
     end
 
+    #
+    # Returns true if the address is a link local address
+    #
+    def link_local?
+      @groups[0] == 0xfe80
+    end
+
     # 
     # Returns true if the address is an unspecified address
     # 

test/ipaddress/ipv6_test.rb

@@ -200,6 +200,12 @@ class IPv6Test < Minitest::Test
     assert_equal "1::1", @klass.new("1:0:0:0:0:0:0:1").compressed
   end
   
+  def test_method_link_local?
+    assert_equal true, @klass.new("fe80::1").link_local?
+    assert_equal true, @klass.new("fe80:ffff::1").link_local?
+    assert_equal false, @klass.new("fe81::1").link_local?
+  end
+
   def test_method_unspecified?
     assert_equal true, @klass.new("::").unspecified?
     assert_equal false, @ip.unspecified?