[MOD] make external link icon to use icon set

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@52969 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] background url-s were throwing file not found errors

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@52970 b456876b-0849-0410-b77d-98878d47e9d5