* Allow fetching all revisions from transwiki Special:Import

* Allow fetching all revisions from transwiki Special:Import
* Allow fetching all revisions from Special:Export GET request
* Disable output buffering on Special:Export; should help with streaming
  large numbers of history items.
* Allow setting a maximum number of revisions for history Special:Export;
  pages with more than $wgExportMaxHistory revisions are excluded from
  export when history is requested.
* Fix transwiki import of pages with space in name