TYPO3 Core

with the new skin links in BE are not underlined anymore, that makes it hard
to find out that f.i. the words 'TYPO3 security team!' on the 'import
extensions' page in EM have a link that opens the security team page on
typo3.org.
I was pointed to this by a user who told me that there would't be a link to
the security team in the extension manager.

re-enable 'text-decoration: underline;' for links in BE
(issue imported from #M6505)