trusted info leaks into safe interp via TIP 280

Save demo script in a file
and [source] in a trusted
interp:

interp create -safe slave
puts [slave eval {
return -level 0 "I know about [dict get [info frame 0] file]"
}]

This demonstrates filesystem
information leaking in the
safe interp.

Since [glob] is denied to a
safe interp, it seems that such
information is meant to be denied.