Import / Contacts gets wrong max upload file size (doesn't use singleton CRM_Core_Config object)

The Import / Contacts wizard always reports the maximum file upload size as 1Mb, regardless
of what's in the php.ini file. The problem seems to be that CRM/Core/Config.php uses

$config =& new CRM_Core_Config();

instead of

$config =& CRM_Core_Config::singleton();

There are several other files where the the singleton is not used.

CRM/Contribute/Import/Form/UploadFile.php
CRM/Core/BAO/DomainDump.php
CRM/History/Import/Form/UploadFile.php
CRM/Import/Form/UploadFile.php
CRM/Member/Import/Form/UploadFile.php
CRM/Utils/Address/USPS.php