Mapster32: in e.g. F5 "next free tag" display, note object w/ greatest tag.

git-svn-id: http://svn.eduke32.com/eduke32@4464 1a8010ca-5511-0410-912e-c29ae57300e0
Mapster32: in linking tag determination, handle 'on' switch picnums (+1).

git-svn-id: http://svn.eduke32.com/eduke32@4465 1a8010ca-5511-0410-912e-c29ae57300e0