Positional attributes for shortcodes

[tellyworth]

The shortcode API introduced with the gallery feature supports attributes like this:

[mytag foo=1 bar="baz"]

This patch adds support for positional attributes like this:

[mytag foo bar]

Positional attributes are included in the $atts array with numeric keys. It's possible to use quotes for attributes that contain spaces, and to mix positional and named attributes:

[mytag "foo bar" baz="bing" asdf]

This would produce the $atts array( 0 => 'foo bar', 'baz' => 'bing', 1 => 'asdf').

Unit tests are here:

​http://svn.automattic.com/wordpress-tests/wp-testcase/test_shortcode.php

[ryan]

(In [6911]) Support positional attributes in shortcodes. Props tellyworth. fixes #5914