[elpa] externals/org updated (4ff4828944 -> e87ecf88be)

[ELPA Syncer]

elpasync pushed a change to branch externals/org.

      from  4ff4828944 org-footnote--collect-references: Fix infinite recursion
       new  9cce40c94f org-link: Customizable preview API for arbitrary link 
types
       new  e87ecf88be Document preview API for arbitrary link types


Summary of changes:
 doc/org-manual.org            | 293 +++++++++++++-------
 etc/ORG-NEWS                  |  93 ++++++-
 lisp/ol.el                    | 603 +++++++++++++++++++++++++++++++++++++++++-
 lisp/org-attach.el            |  11 +-
 lisp/org-compat.el            | 185 +++++++++++++
 lisp/org-cycle.el             |  31 ++-
 lisp/org-keys.el              |   7 +-
 lisp/org-plot.el              |   2 +-
 lisp/org.el                   | 554 ++------------------------------------
 testing/lisp/test-org-fold.el |   4 +-
 10 files changed, 1120 insertions(+), 663 deletions(-)