Fix Mime::Type#=~ not using Regexp.quote

Signed-off-by: NPratik Naik <pratiknaik@gmail.com>

actionpack/lib/action_controller/mime_type.rb

@@ -178,7 +178,7 @@ def ==(mime_type)
 
     def =~(mime_type)
       return false if mime_type.blank?
-      regexp = Regexp.new(mime_type.to_s)
+      regexp = Regexp.new(Regexp.quote(mime_type.to_s))
       (@synonyms + [ self ]).any? do |synonym|
         synonym.to_s =~ regexp
       end

actionpack/test/controller/mime_type_test.rb

@@ -88,5 +88,6 @@ def test_regexp_matcher
     assert Mime::JS !~ "text/html"
     assert !(Mime::JS !~ "text/javascript")
     assert !(Mime::JS !~ "application/javascript")
+    assert Mime::HTML =~ 'application/xhtml+xml'
   end
 end