Change <deprecated/> node to attribute of either entry or signature and add category when not there

[kswedberg]

Most deprecated entries have <deprecated> inside either <entry> or <signature>. We need to remove those and use attributes of <entry> or <signature> instead.

Also, make sure those entries have a deprecated category assigned to them.

[kswedberg]

Actually, we're killing the "deprecated" category altogether. Please remove it from all entries, and remove the category from categories.xml in the root directory.