Remove autoloads for constants no longer shipped with rack

Removes the following autoloads:

* File
* Handler
* Server
* Auth::Digest

Sort the remaining autoloads alphabetically.

Fixes #2112

lib/rack.rb

@@ -16,22 +16,20 @@
 
 module Rack
   autoload :BadRequest, "rack/bad_request"
-  autoload :Builder, "rack/builder"
   autoload :BodyProxy, "rack/body_proxy"
+  autoload :Builder, "rack/builder"
   autoload :Cascade, "rack/cascade"
   autoload :CommonLogger, "rack/common_logger"
   autoload :ConditionalGet, "rack/conditional_get"
   autoload :Config, "rack/config"
   autoload :ContentLength, "rack/content_length"
   autoload :ContentType, "rack/content_type"
+  autoload :Deflater, "rack/deflater"
+  autoload :Directory, "rack/directory"
   autoload :ETag, "rack/etag"
   autoload :Events, "rack/events"
-  autoload :File, "rack/file"
   autoload :Files, "rack/files"
-  autoload :Deflater, "rack/deflater"
-  autoload :Directory, "rack/directory"
   autoload :ForwardRequest, "rack/recursive"
-  autoload :Handler, "rack/handler"
   autoload :Head, "rack/head"
   autoload :Headers, "rack/headers"
   autoload :Lint, "rack/lint"
@@ -40,32 +38,28 @@ module Rack
   autoload :MediaType, "rack/media_type"
   autoload :MethodOverride, "rack/method_override"
   autoload :Mime, "rack/mime"
+  autoload :MockRequest, "rack/mock_request"
+  autoload :MockResponse, "rack/mock_response"
+  autoload :Multipart, "rack/multipart"
   autoload :NullLogger, "rack/null_logger"
   autoload :QueryParser, "rack/query_parser"
   autoload :Recursive, "rack/recursive"
   autoload :Reloader, "rack/reloader"
+  autoload :Request, "rack/request"
+  autoload :Response, "rack/response"
   autoload :RewindableInput, "rack/rewindable_input"
   autoload :Runtime, "rack/runtime"
   autoload :Sendfile, "rack/sendfile"
-  autoload :Server, "rack/server"
   autoload :ShowExceptions, "rack/show_exceptions"
   autoload :ShowStatus, "rack/show_status"
   autoload :Static, "rack/static"
   autoload :TempfileReaper, "rack/tempfile_reaper"
   autoload :URLMap, "rack/urlmap"
   autoload :Utils, "rack/utils"
-  autoload :Multipart, "rack/multipart"
-
-  autoload :MockRequest, "rack/mock_request"
-  autoload :MockResponse, "rack/mock_response"
-
-  autoload :Request, "rack/request"
-  autoload :Response, "rack/response"
 
   module Auth
     autoload :Basic, "rack/auth/basic"
-    autoload :AbstractRequest, "rack/auth/abstract/request"
     autoload :AbstractHandler, "rack/auth/abstract/handler"
-    autoload :Digest, "rack/auth/digest"
+    autoload :AbstractRequest, "rack/auth/abstract/request"
   end
 end