Infinite Scroll: keep track of $currentday between IS requests
Basically, at each new IS query, we want the global $previousday to be set to the previous query's $currentday value. This allows the_date() to work consistently across IS requests.
Major props @mcsf
Genericons: Bump RTL file
Widget Conditions: Merge fix for old-style widgets
Previous changeset breaks widgets that have no settings.
Props @mjangda
See: #21
Merge pull request #117 from Automattic/merge-20140122

Continuing merge from upstream