Improve manual for table formulas

* doc/org.texi (Field coordinates in formulas): Rephrase and add an
example with a Lisp formula to copy from remote table.
Merge branch 'master' of orgmode.org:org-mode
org-element: Update paragraph separate regexp

* lisp/org-element.el (org-element-paragraph-separate): More accurate
  regexp.
ox-publish: Error when publishing non-existent file

* lisp/ox-publish.el (org-publish-cache-ctime-of-src): Return an error
  when publishing a non-existent file.

Suggested-by: Arne Babenhauserheide <arne_bab@web.de>
Merge branch 'maint'
Merge branch 'master' of orgmode.org:org-mode
Fix problem with :exact-positions in capture

* lisp/org-capture.el (org-capture-place-entry): Set :exact-position
before doing other stuff, to allow function with other target settings

TINYCHANGE

Assuming file "test.org" has a single headline "* Level 1" (ended with
newline character), when trying to use function type capture target in
an org-capture template, as shown in the example:

(setq org-capture-templates
      `(("t"
         "Test function type target"
         entry
         (function
          (lambda ()
            (set-buffer (org-capture-target-buffer "test.org"))
            (goto-char (point-max))))
         "* Level 2")))

When this template gets filled, file "test.org" becomes:

* Level 1
* Level 2

Instead of:

* Level 1
** Level 2

This is because when using function type target, `:exact-position' is
used to store buffer position returned by user's function (the lambda
function here), and function `org-capture-place-entry' will never
insert template as a child of current entry when `:exact-position' is
used.

The problem is addressed by not special casing for `:exact-position'
in function `org-capture-place-entry'.

York
Fix bug in uncompilation of column format

* lisp/org-colview.el (org-columns-uncompile-format): Fix bug when retrieving
operator symbol.
org-element: Prepare signature change

* lisp/ob-exp.el: Declare signature change.
* lisp/org-macro.el: Declare signature change.
* lisp/org.el (org-backward-element, org-drag-element-backward): Avoid
  using optional argument from `org-element-at-point'.
* testing/lisp/test-org-element.el: Update test.
org-element: Speed-up for `org-element-at-point'

* lisp/org-element.el (org-element-at-point): Rewrite function. Remove
  optional argument.

Include an opportunistic search at the beginning of the function.  It
drastically improves speed on large sections for a small overhead on
small ones.
org-colview: Silence byte-compiler
org-element: Optimize parser only when cache is active

* lisp/org-element.el (org-element-at-point): Try opportunistic
  shortcut only when cache is active.
Remove support for legacy (?) code blocks
Add org-debbugs.el.
* contrib/lisp/org-debbugs.el (org-debbugs-mode-map): docstring comes last.