Accessibility: Avoid Adjacent Duplicate Links for Topic Author

[dcavins]

When a user's avatar is inserted before the user's name in the topic or forum loops, each item is individually wrapped in a link with the same destination. WCAG prefers that these items be contained within a single link: ​https://www.w3.org/TR/2014/NOTE-WCAG20-TECHS-20140311/H2

I've attached a patch that updates the HTML output from:

<a href="http://bptest.local/members/admin/" title="View Cap’n's profile" class="bbp-author-avatar">
	<img alt="" src="//www.gravatar.com/avatar/3665d8d0d1b0eb151f8e941070fad664?s=14&amp;r=g&amp;d=mm" srcset="//www.gravatar.com/avatar/3665d8d0d1b0eb151f8e941070fad664?s=14&amp;r=g&amp;d=mm 2x" class="avatar avatar-14 photo" width="14" height="14">
</a>&nbsp;
<a href="http://bptest.local/members/admin/" title="View Cap’n's profile" class="bbp-author-name">Cap’n</a>

to

<a href="http://bptest.local/members/admin/" title="View Cap’n's profile" class="bbp-author-link">
	<span class="bbp-author-avatar">
		<img alt="" src="//www.gravatar.com/avatar/3665d8d0d1b0eb151f8e941070fad664?s=14&amp;r=g&amp;d=mm" srcset="//www.gravatar.com/avatar/3665d8d0d1b0eb151f8e941070fad664?s=14&amp;r=g&amp;d=mm 2x" class="avatar avatar-14 photo" width="14" height="14">
	</span>&nbsp;
	<span class="bbp-author-name">Cap’n</span>
</a>

Thanks for considering this enhancement.

[dcavins]

Replace adjacent duplicate links.

[johnjamesjacoby]

In 6868:

Accessibility: Avoid back-to-back author links.

This change ensures that avatar and display-name links are wrapped in a shared anchor, instead of each with their own.

Includes a few test changes to better suit our intentions of verifying valid & accessible HTML output.

Fixes #3220. Props dcavins.