`fe80` should be case insensitive too

lib/resolv.rb

@@ -2462,7 +2462,7 @@ class Resolv
     ##
     # IPv6 link local address format fe80:b:c:d:e:f:g:h%em1
     Regex_8HexLinkLocal = /\A
-      fe80
+      [Ff][Ee]80
       (?::[0-9A-Fa-f]{1,4}){7}
       %[0-9A-Za-z]+
       \z/x
@@ -2471,7 +2471,7 @@ class Resolv
     # Compressed IPv6 link local address format fe80::b%em1
 
     Regex_CompressedHexLinkLocal = /\A
-      fe80:
+      [Ff][Ee]80:
       (?:
         ((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?) ::
         ((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?)

test/resolv/test_addr.rb

@@ -25,6 +25,9 @@ class TestResolvAddr < Test::Unit::TestCase
     assert_match(Resolv::IPv6::Regex, "fe80:2:3:4:5:6:7:8%em1", bug17112)
     assert_match(Resolv::IPv6::Regex, "fe80::20d:3aff:fe7d:9760%eth0", bug17112)
     assert_match(Resolv::IPv6::Regex, "fe80::1%em1", bug17112)
+    assert_match(Resolv::IPv6::Regex, "FE80:2:3:4:5:6:7:8%EM1", bug17112)
+    assert_match(Resolv::IPv6::Regex, "FE80::20D:3AFF:FE7D:9760%ETH0", bug17112)
+    assert_match(Resolv::IPv6::Regex, "FE80::1%EM1", bug17112)
   end
 
   def test_valid_socket_ip_address_list