Merge Changes made in Gnus master

Merge Changes made in Gnus master

2013-07-30 Lars Magne Ingebrigtsen <larsi@gnus.org>
  * gnus-start.el (gnus-read-active-for-groups): Always mark the data as
  dirty to ensure nnimap data being saved.

2013-07-30 Tassilo Horn <tsdh@gnu.org>
  * gnus-sum.el (gnus-summary-make-menu-bar): Add "Current thread score"
  menu entry.
  * gnus-score.el (gnus-summary-current-score): Use prefix arg to show
  the current thread's total score instead of the current article's
  score.