SpecialRecentchanges: Repair recentchangestext in content language

* Use getHtmlCode() instead of getCode() to generate a BCP 47 conform
  HTML lang attribute.
* Use <div> instead of <p> because the <p> gets rendered as

<p lang="en" dir="ltr"></p>
<p>Text</p>
<p></p>

and the <div> gets rendered as

<div lang="en" dir="ltr">
<p>Text</p>
</div>

* Set $lineStart = true

Change-Id: I62ce26ba550fb25bc2e770186cea3435374bb4e6
Merge "SpecialRecentchanges: Repair recentchangestext in content language"