The database that holds the pubsub items has a limited size for its payload. For HSQLDB, this is limited to 4000 characters.
As PEP is used to store binary data (avatars), the size should be increased dramatically.
Only the column size of the database types 'hsqldb' and 'oracle' seems limited to a varchar of limited size. All other databases use clob or text like data types.
Mysql is using MEDIUMTEXT, which is limited to 16MB. Let's change that too.