Zabbix

A...I..... [ZBXNEXT-6196] increased storage size of fields "description", "headers", "params" and "posts" for items, item prototypes and discovery rules for Oracle backend

Merge in ZBX/zabbix from feature/ZBXNEXT-6196-5.1 to master

* commit '2a950d5245cc2bd2a36da1a52f964d3c67785235':
  .......... [ZBXNEXT-6196] updated changelog
  A......... [ZBXNEXT-6196] replaced hardcoded field names by use database schema; sligtly improved memory consumption and performance
  .D..I..... [ZBXNEXT-6196] fixed formatting of the database scheme; fixed ChangeLog entry
  .......... [ZBXNEXT-6196] added changelog
  A...I..... [ZBXNEXT-6196] upgrade patch; api nclob type field added to result with separate database query