Add `:caption' attribute to #+ATTR_LATEX property
* lisp/ox-latex.el (org-latex--caption/label-string): Add ability,
which can build a caption string from `:caption' attribute of #+ATTR_LATEX.
(org-latex--inline-image,org-latex--org-table): Tiny change.
* doc/org.texi (@LaTeX{} specific attributes): Document `:caption'
attribute of #+ATTR_LATEX.
This feature is very useful when you export org to latex with custom
caption command, for example:
\#+ATTR_LATEX: :caption \BiTableCaption{caption 1}{caption 2}
|---+---|
| x | y |
|---+---|
| 1 | 2 |
|---+---|