Improve documentation of TOC placement.

* doc/org.texi: (Table of contents) Improve documentation of TOC placement.
lisp/org.el: Do not inline images when no graphic display is available

* lisp/org.el (org-preview-latex-fragment)
(org-display-inline-images): Detect whether a graphic display is
available before inlining images to prevent an error.

Thanks to Rick Frankel for the report and the solution.

> `org-startup-with-inline-images' is a customizable variable. The
> problem is that if an org file is visited in a non-graphics buffer (or
> batch), `org-display-inline-images' is called an throws an error
> ("Non-X frame used").
>
> This problem also occurs when e.g., `org-babel-after-execute-hook' is
> set to 'org-display-inline-images (which can be mitigated by not
> setting the hook in a non-x frame).
>
> Since the startup variable is a customization, and causes problems if
> not set programatically, IMHO, the best solution would be to wrap the
> `org-display-inline-images' function in a test so that is is a no-op
> on non graphic displays:
ox: Cache locations of fuzzy links

* ox.el (org-export-resolve-fuzzy-link): Look for fuzzy link in a
  cache before trying to resolve it in the parse tree.

When a document contains a large number of identical fuzzy links, it
doesn't make sense to continually search for them.  Instead, cache the
locations in the position independent case.
Merge branch 'maint'
ox-latex.el (org-latex-headline): Don’t insert alternate title if identical to regular one

* lisp/ox-latex.el (org-latex-headline): Don’t insert alternate title if
  identical to regular one.
Merge branch 'maint'
ox-taskjuggler.el: Handle the case of an empty document title

* ox-taskjuggler.el (org-taskjuggler-project-plan): Use the
project name as the title of the (default) report if the
document title is empty.

Thanks to Eric S Fraga for reporting this bug.
ox: Fix caching for fuzzy link resolution

* lisp/ox.el (org-export-resolve-fuzzy-link): Fix caching process.
* testing/lisp/test-ox.el: Add test.
Merge branch 'maint'