org.el (org-insert-heading): Fix case when there the first heading starts at the beginning of the buffer

* org.el (org-insert-heading): Fix case when there the first
heading starts at the beginning of the buffer.

In this case, `org-backward-heading-same-level' will throw an error in
the let form, and the error would fall back on "*" instead of falling
back on the correct number of stars to add.

Thanks to Jisang Yoo and John Hendy who reported this bug.
Merge branch 'maint'
org-element: Fix interpretation of empty fixed-width elements

* lisp/org-element.el (org-element-fixed-width-interpreter): Fix
  interpretation of fixed-width elements with a nil or empty string
  value.
* testing/lisp/test-org-element.el: Add tests.
Merge branch 'maint'
ox-taskjuggler.el: Replace %title in default reports by document title

* ox-taskjuggler.el (org-taskjuggler-default-reports)
(org-taskjuggler-project-plan): If the default reports contain
%title it will be replaced with the document title.

This is based on a suggestion by John Hendy.
ox-taskjuggler.el: Improve doc strings

* ox-taskjuggler.el (org-taskjuggler-process-command): Improve doc
string.
ox-taskjuggler.el: Resolve dependencies also against ID property

* ox-taskjuggler.el (org-taskjuggler-resolve-dependencies): When
resolving dependencies do not only look for matching task_id
properties but also for the standard ID property.

That way the user can make use of the standard org-id functionality to
create unique ids for a task and yanking the id in another task as a
BLOCKER.
Merge branch 'master' of orgmode.org:org-mode
Use @var{} only for metasyntactical meanings in the manual.

Thanks to Suvayu Ali for the patch
org-list: Properly update `org-list-allow-alphabetical'

* lisp/org-list.el (org-list-allow-alphabetical): Properly update
  `org-list-allow-alphabetical' when changed after org.el has been
  loaded.
Merge branch 'maint'
Fix error when filling a table from an affiliated keyword

* lisp/org.el (org-fill-paragraph): Move to table beginning before
  aligning the table when M-q is called from an affiliated keyword.
* testing/lisp/test-org.el: Add test.
Merge branch 'maint'
ox-org: Preserve affiliated keywords

* lisp/ox.el (org-export-expand): Optionally add affiliated keywords
  to results.
* lisp/ox-org.el (org-org-identity): Use new argument for
  `org-export-expand'.
Merge branch 'maint'
Speed-up `org-insert-heading'

* lisp/org.el (org-insert-heading): Refactor to use `org-in-item-p'
  only once.
Use @var{} only for metasyntactical meanings in the manual.

Thanks to Suvayu Ali for the patch
Merge branch 'maint'