Add tests for realm case sensitivity in AuthChallenge

As per RFC 1945 (section 11) and RFC 2617, the realm value is case sensitive.
This commit adds tests for realm case sensitivity in
Mechanize::HTTP::AuthChallenge.

test/test_mechanize_http_auth_challenge.rb

@@ -25,6 +25,14 @@ def test_realm_digest
     assert_equal expected, @challenge.realm(@uri + '/foo')
   end
 
+  def test_realm_digest_case
+    challenge = @AC.new 'Digest', { 'realm' => 'R' }, 'Digest realm=R'
+
+    expected = @AR.new 'Digest', @uri, 'R'
+
+    assert_equal expected, challenge.realm(@uri + '/foo')
+  end
+
   def test_realm_unknown
     @challenge.scheme = 'Unknown'
 
@@ -39,6 +47,12 @@ def test_realm_name
     assert_equal 'r', @challenge.realm_name
   end
 
+  def test_realm_name_case
+    challenge = @AC.new 'Digest', { 'realm' => 'R' }, 'Digest realm=R'
+
+    assert_equal 'R', challenge.realm_name
+  end
+
   def test_realm_name_ntlm
     challenge = @AC.new 'Negotiate, NTLM'