Bug #1055232
CVE-2012-2243

Before this patch, if a user uploaded HTML or XML files
then tried to download them, or linked other users to download
them, they would be presented with an escaped version along
with a link to download the original.

This did not include XHTML files, which can cause the same
security issues as HTML or XML files. This patch includes the
XHTML mimetype of application/xhtml+xml in the test of which
files to escape.

Change-Id: Iffb8308fdb56a173fd4af2bbda800999dd11fea3
Signed-off-by: Hugh Davenport <hugh@catalyst.net.nz>