Image captions break when wpautop is disabled in the editor

[azaozz]

By default wpautop is enabled in TinyMCE but can be turned off when using wp_editor(). This stops running the JS pre_wpautop() on saving the post content and enables some basic HTML source formatting.

This breaks the regexp that converts the <div><dl>...</dl></div> back to a caption shortcode.

[azaozz]

Seems this is not a regression on 4.0 but rather a change in the latest TinyMCE. So

<div><dl>
...
</dl></div>

turns into

<div>
<dl>
...
</dl>
</div>

[azaozz]

In 29592.patch:

• Grab white space around the <dl> tag when converting it to image caption shortcode.
• Relax the test for broken shortcodes.

[azaozz]

In 29730:

TinyMCE: fix image captions regexp when wpautop is disabled in wp_editor(). Fixes #29592 for trunk.

[azaozz]

Reopen for 4.0.1.

[nacin]

In 30406:

TinyMCE: fix image captions regexp when wpautop is disabled in wp_editor().

Merges [29730] to the 4.0 branch.

props azaozz.
fixes #29592.