ox-html.el (org-html-format-inline-image): Fix missing string in formatting string

* ox-html.el (org-html-format-inline-image): Fix missing string in
formatting string.

Thanks to Richard Stanton for reporting this.
contrib/lisp/org-expiry.el (org-expiry-inactive-timestamps): Fix docstring

* contrib/lisp/org-expiry.el (org-expiry-inactive-timestamps):
Fix docstring.
org.el (org-insert-heading): DTRT when in a narrowed region

* org.el (org-insert-heading): DTRT when in a narrowed region.

* org-compat.el (org-buffer-narrowed-p): New compatibility
function.

Thanks to Samuel Wales for reporting this problem.
testing/: Merge org-test-ob-consts.el into org-test.el
ox-html.el (org-html-link): Minor code clean-up

* ox-html.el (org-html-link): Minor code clean-up.
testing/lisp/text-ox.el: Comment two tests out

These tests fail when run in batch mode:

`test-org-export/define-derived-backend'
`test-org-export/derived-backend-p'

They don't fail when run interactively.
Let's comment them out until we understand
what's wrong with these tests.