Allow C-c C-c to act on item anywhere on its first line

* lisp/org.el (org-ctrl-c-ctrl-c): Anywhere on the first line of an
  item, act on that item, provided no other object is found under the
  point.  Fix bug when function is called on a footnote definition
  attribute.

This is a convenience feature mimicing old behaviour, but it is an
aberration from the structure POV.
Revert "org-element: Change return value for element at point in some corner cases"

This reverts commit 13e49a63853b95e6033e3e3230dda0b824bc350a.

Conflicts:
	lisp/org-element.el
Fix C-c C-c error when called on attributes attached to a plain list

* lisp/org.el (org-ctrl-c-ctrl-c): Fix error when called on attributes
  attached to a plain list.
org.el (org-adaptive-fill-function): Fix various bugs when filling in message-mode

* org.el (org-adaptive-fill-function): In message-mode, don't
lines in the message header, nor table lines in the body.
Correctly fill lines starting with `org-outline-regexp' in the
body.
Merge branch 'maint'

Conflicts:
	lisp/org.el
org-install.el: Do not warn users.

* org-install.el: Do not warn users.
Merge branch 'maint'
org-agenda.el (org-agenda-quit): Delete indirect buffer's window only when it exists

* org-agenda.el (org-agenda-quit): Delete indirect buffer's window
only when it exists.

When indirect buffer's window doesn't exist, the original logic will
delete the current window.

TINYCHANGE
Merge branch 'maint'
org.el: fix error message when C-u C-u C-c C-c on a list.

* org.el (org-ctrl-c-ctrl-c): Only throw a message when using
two universal prefix arguments on a list where all items are
already in a transitory state.  Refine the error when the
checkbox cannot be toggled.

Thanks to Robert Horn for reporting this.
org-agenda.el: Let-bind `org-time-clocksum-use-effort-durations' when checking clocks and formatting items

* org-agenda.el (org-agenda-show-clocking-issues)
(org-agenda-format-item): Let-bind
`org-time-clocksum-use-effort-durations' to nil.

Thanks to Vincent Beffara for reporting this.
Small typo correction

TINYCHANGE
org.texi (Checkboxes, Radio lists): Fix typos

* org.texi (Checkboxes, Radio lists): Fix typos.
Merge branch 'maint'
org.texi (Built-in table editor): Tiny enhancement

* org.texi (Checkboxes, Radio lists): Fix typos.

Thanks to Xue Fuqiao for pointing this.
org-agenda.el (org-agenda-skip): Correctly handle commented out scheduled/deadline lines

* org-agenda.el (org-agenda-skip): Correctly handle commented
out scheduled/deadline lines.  Refactor.

Thanks to Rainer Stengele for reporting this and to Nick Dokos for
investigating further.  This fix will not slow down the agenda as checking
for a text property seems equally fast (and perhaps even slightly faster)
than checking the character after.
Merge branch 'maint'
org-agenda.el (org-agenda-get-deadlines): Fix bug: use `org-agenda-show-inherited-tags'

* org-agenda.el (org-agenda-get-deadlines): Fix bug: use
`org-agenda-show-inherited-tags'.

Thanks to Kiwon Um for reporting this.
Merge branch 'maint'

Conflicts:
	lisp/org-agenda.el
org-element.el (org-element-at-point): Fix typo in docstring

* org-element.el (org-element-at-point): Fix typo in docstring.