Add a space after "View Inline" in mail to prevent double-click on the filename from selecting "Inline"

Summary:
See PHI920. Ref T13210. Since the HTML is just:

```
<a>View Inline</a><span>filename.txt</span>
```

..double-clicking "filename.txt" in email selects "Inlinefilename.txt".

Add a space to stop this. At least in Safari, a space between the tags is not sufficient (perhaps because the parent is a `<div>`?). I couldn't find an authoritative-seeming source on what the rules for this actually are and adding a space here fixes the issue without changing the visual rendering, so just put it here.

Test Plan:
  - Made an inline.
  - Used `bin/mail show-outbound --id ... --dump-html` to dump the HTML.
  - Double-clicked the filename.

{F5929186}

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13210

Differential Revision: https://secure.phabricator.com/D19742

src/applications/differential/mail/DifferentialInlineCommentMailView.php

@@ -446,7 +446,18 @@ final class DifferentialInlineCommentMailView
             'style' => implode(' ', $link_style),
             'href' => $link_href,
           ),
-          pht('View Inline'));
+          array(
+            pht('View Inline'),
+
+            // See PHI920. Add a space after the link so we render this into
+            // the document:
+            //
+            //   View Inline filename.txt
+            //
+            // Otherwise, we render "Inlinefilename.txt" and double-clicking
+            // the file name selects the word "Inline" as well.
+            ' ',
+          ));
       } else {
         $link = null;
       }