Make 'Display Upload Progress' optional.

src/Posting/QR.coffee

@@ -662,7 +662,8 @@ QR =
           ) %>
     extra =
       form: $.formData formData
-      upCallbacks:
+    if Conf['Show Upload Progress']
+      extra.upCallbacks =
         onload: ->
           # Upload done, waiting for server response.
           QR.req.isUploadFinished = true

src/config/Config.coffee

@@ -461,6 +461,11 @@ Config =
         'Show the classic name, email, and subject fields in the QR, even when 4chan doesn\'t use them all.'
         1
       ]
+      'Show Upload Progress': [
+        true
+        'Track progress of file uploads as percentage in submit button.'
+        1
+      ]
       'Cooldown': [
         true
         'Indicate the remaining time before posting again.'