some more minor incompatibilties 7.2 <-> 7.3

I noticed some other minor differences between 7.2 and 7.3:
* 7.2: select now() + '1 minute'::timespan => works
* 7.2: select now() + '1 minute'::reltime => works
* 7.3: select now() + '1 minute'::timespan => does not work (Type "timespan" does not exist)
* 7.3  select now() + '1 minute'::reltime => works

So timespan is no longer supported I guess, but reltime will work as well. Is there a compatibility or migration
sectionin the documentation that might help users to handle this? 
Maybe we can collect such reports and prepare a upgrade tutorial?

Regards,Mario