What it does: This patch adds the function show_security_icon to ljlib.pl. The function is given a security setting ("private" or "usemask") and outputs the HTML to display the security icon. The patch modifies talkpost.bml and talkread.bml to use the show_security_icon function in front of the subject line.
Test it (log in using user=test pass=test):
talkpost.bml: (protected) (private) (no subject) (public, no subject)
talkread.bml: (protected) (private) (no subject) (public, no subject)
(Update: I made a minor edit. Now the icon is on its own line if there is no subject.)