org-element: Interpret headlines without a `:pre-blank' property

* contrib/lisp/org-element.el (org-element-headline-interpreter):
  Interpret headlines without a `:pre-blank' property.
spelling fixes

* org.el (org-create-formula-image-with-imagemagick): Fix typo.
Using 'call-process to launch latex program

* org.el (org-create-formula-image-with-imagemagick): Use 'call-process
to launch latex so that no shell output buffer will be shown when previewing
formulas.
Merge branch 'master' of orgmode.org:org-mode
org-element: Internally store headline/inlinetask's tags as a list of strings

* contrib/lisp/org-element.el (org-element-headline-parser,
  org-element-headline-interpreter, org-element-inlinetask-parser,
  org-element-inlinetask-interpreter): Store headline/inlinetask's
  tags as a list of strings.
* contrib/lisp/org-export.el (org-export--selected-trees,
  org-export--skip-p): Use new tag representation.
* contrib/lisp/org-e-ascii.el (org-e-ascii--build-title,
  org-e-ascii-format-inlinetask-function, org-e-ascii-inlinetask): Use
  new tag representation.
* contrib/lisp/org-e-html.el (org-e-html-format-headline-function,
  org-e-html-format-inlinetask-function, org-e-html--tags): Use new
  tag representation.
* contrib/lisp/org-e-latex.el (org-e-latex-format-headline-function,
  org-e-latex-format-inlinetask-function, org-e-latex-headline,
  org-e-latex-inlinetask): Use new tag representation.
* contrib/lisp/org-e-odt.el (org-e-odt-format-org-tags): Use new tag
  representation.
* testing/lisp/test-org-element.el: Update test.
* lisp/org.el (org-translate-link): Fix bug
* lisp/org.el (org-link-expand-abbrev): Fix docstring
Merge branch 'maint'
org-element: Apply `org-translate-link' when parsing a link

* contrib/lisp/org-element.el (org-element-link-parser): Apply
  `org-translate-link' when parsing a link.
* testing/lisp/test-org-element.el: Add test.
Rework `orgstruct++-mode' so that you can turn if off safely.

* org.el (org-auto-fill-fallback-function)
(org-indent-line-fallback-function)
(org-fill-paragraph-fallback-function)
(org-auto-fill-fallback-function)
(org-indent-line-fallback-function)
(org-fill-paragraph-fallback-function): Remove.
(org-fb-vars): New buffer-local variable.
(orgstruct++-mode): Use the fallback variable `org-fb-vars' to
store, use and restore variables if needed.
(org-fill-paragraph): Ignore `orgstruct++-mode' filling
variables when needed.
(org-auto-fill-function, org-indent-line-function): Ditto.

* org-macs.el (orgstruct++-ignore-org-filling): New macro.
Merge branch 'fix-orgstruct'
Merge branch 'master' of orgmode.org:org-mode
Fix bugs about computing durations in the column view.

* org-colview.el (org-columns-string-to-number): When
computing the values for the colview, match durations and
convert them to HH:MM values.

* org.el (org-duration-string-to-minutes): Match non-round
numbers.  Add a new optional parameter to allow returning the
output as a string.

Thanks to Sébastien for reporting these bugs.
org.texi (Durations and time values): Fix typo.

* org.texi (Durations and time values): Fix typo.
Merge branch 'maint'
org-table.el: Fix bug about handling a negative duration value.

* org-table.el (org-table-time-seconds-to-string): Fix bug
about handling a negative duration value.
Merge branch 'maint'