...G...PS. [ZBX-8494] added check to prevent starting a proxy with a server database and vice versa

Before this change:
   - the proxy crashed when started with a database prepared for Zabbix server.

After this change:
   - server checks is it started with server database,
   - proxy checks is it started with proxy database,
   - if wrong type of database is detected, the server or proxy terminates.
   - a number of function prototypes have been fixed in server, proxy and agent.