Add test for print relative for page that doesn't exist

An example where this can happen is a link to a page that was renamed
and redirected, or just a normal HTML file.

Author: ehuss

tests/testsuite/print/relative_links/expected/print.html

@@ -9,6 +9,10 @@ <h1 id="testing-relative-links-for-the-print-page"><a class="header" href="#test
 <p>A <a href="#some-section">fragment link</a> should work.</p>
 <p>Link <a href="../std/foo/bar.html">outside</a>.</p>
 <p>Link <a href="../std/foo/bar.html#panic">outside with anchor</a>.</p>
+<p>Link <a href="../first/alpha/beta.html">inside but doesn’t exist</a>.
+Link <a href="#anchor">inside but doesn’t exist with anchor</a>.
+Link <a href="../first/alpha/gamma.html">inside to html</a>.
+Link <a href="#anchor">inside to html with anchor</a>.</p>
 <p><img src="images/picture.png" alt="Some image"></p>
 <p><a href="#first-nested">HTML Link</a></p>
 <img src="images/picture.png" alt="raw html">

tests/testsuite/print/relative_links/src/second/nested.md

@@ -11,6 +11,11 @@ Link [outside](../../std/foo/bar.html).
 
 Link [outside with anchor](../../std/foo/bar.html#panic).
 
+Link [inside but doesn't exist](../first/alpha/beta.md).
+Link [inside but doesn't exist with anchor](../first/alpha/beta.md#anchor).
+Link [inside to html](../first/alpha/gamma.html).
+Link [inside to html with anchor](../first/alpha/gamma.html#anchor).
+
 ![Some image](../images/picture.png)
 
 <a href="../first/nested.md">HTML Link</a>