Allow usage of uppercase 'ASC'/'DESC' to order in shortcode_speakers

[pixolin]

I got somewhat confused when using the shortcode to list speakers on the website for our WordCamp Cologne:

I added a parameter order="ASC" as I usually do when adding a new WP_Query() in a template, but to no avail. After several attempts I looked into the plugin source code and found out, the shortcode [speakers] only accepts the parameter order in lowercase, which then gets turned into uppercase by function [parse order](​https://core.trac.wordpress.org/browser/tags/4.2.1/src/wp-includes/query.php#L2311) (introducded in WordPress 3.9).

A simple workaround would be to add $attr['order'] = strtolower( $attr['order'] ); to improve handling of the shortcode.

[pixolin]

Patch for ticket #1016

[pixolin]

Sorry for sending the diff file with wrong file extension. :)

[iandunn]

In 1539:

WordCamp Post Type: Accept shortcode parameters regardless of case.

Fixes #1016
Props pixolin

[iandunn]

This was actually a problem for many parameters across multiple shortcodes, so r1539 expanded on your patch a bit, but wc-post-types.diff was a good first step.

Thanks for taking the time to dig into why this was happening, and then reporting and patching it :)

[iandunn]

In 1540:

WordCamp Post Types: Maintain boolean values during str_to_bool() conversion.

This fixes a bug introduced in r1539 where a boolean passed to this function would be unintentionally converted to a string, but later treated as though it might still be a boolean.

See #1016
See ​https://wordpress.slack.com/archives/meta/p1430769561000761