Twenty Ten/Eleven: Use callback to enqueue scripts and styles

[obenland]

The theme review guidelines require themes to enqueue all stylesheets and scripts, using wp_enqueue_style()/wp_enqueue_script(), and hooked into an appropriate hook via callback function, rather than hard-coding stylesheet/script links or tags in the template.

There might be a backwards compatibility issue when rogue scripts are hooked to 'wp_head' on 0 priority.

[lancewillett]

In 23720:

Twenty Eleven: use callback in functions.php to enqueue scripts and styles rather than putting them directly in header.php template file. Props obenland, see #23772.

[lancewillett]

In 23721:

Twenty Ten: use callback in functions.php to enqueue scripts and styles rather than putting them directly in header.php template file. Props obenland, fixes #23772.

[lancewillett]

Another case of bad news bears, like #23774.

This change isn't backward compatible with child themes, so we need to revert for both Ten and Eleven.

[lancewillett]

In 23778:

Twenty Ten and Twenty Eleven: revert r23720 and r23721 (closes #23772) and r23718 and r23719 (closes #23774).

Unfortunately, it's too late for these improvements in older themes since it's very likely they'll adversely affect child themes.