Fix a few bugs pointed out in issue 0002154 by bevindarkgun bevindarkgun@yahoo.com

• core/string_api.php
  (html_strip_hrefs):
  • fix both regexes to use [^>]> instead of [^\"]
  • make regex searches case insensitive to we pick up anchors with
    A as well as a, etc

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2157 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9