#609772 by dww, JacobSingh, ksenzee: Fixed Impossible to extend the FileTransfer class system in contrib

- Patch #732486 by Damien Tournoud, JacobSingh: drupal_add_http_header()  req ; make Status a normal header and drupal_add_http() header shouldn't return a list of headers.

- Patch #704656 by clemens.tolboom: authorize.php failed to proceed when 'Install from a URL' was selected. Undefined ajax_process_form().

#610290 by dww and sun: system_run_authorized() shouldn't always drupal_goto() so it can be used in submit handlers.

#320331 by Dave Reid, dww, John Morahan, cwgordon7, moshe weitzman, c960657, and smoothify: Turn custom_url_rewrite_inbound() and custom_url_rewrite_outbound() into hooks.

- Patch #605344 by dww: documentation and code style fixes for update manager. This was ready before freeze.

#538660 by JacobSingh, dww, JoshuaRogers, adrian, Crell, chx, anarcat, and cwgordon7: Add a functioning Plugin Manager to core. Can you say module installation and updates through the UI? I knew you could! :D