RichTable at al: links are now detected

I just found and fixed the bug, which prevented some links, esp. for 
plugins but from everywhere else also, to be updated into the links table.

array_merge doesn't handle numeric arrays of arrays, array_unique ditto.
This problem was added when I introduced semantic relations into the 
link structure. But I vaguely remember that RichTable users also 
complained. This should be fixed now.

I also added some cleanup code to the ADODB backend which purges empty, 
non-referenced pagaes from the tables when a link is deleted.
For now only when DEBUG is specified.
-- 
Reini Urban
http://phpwiki.org/
http://helsinki.at/  http://spacemovie.mur.at/