Zabbix

....I..... [ZBX-13350] define various configuration file and directory paths on autoconf level

In addition to getting rid of duplicate path definitions (in the
Makefiles, the code) now the default paths will be printed out after
running ./configure . Added information is:

- default path to configuration file
- default path to externalscripts directory
- default path to alertscripts directory
- default paths to look for cURL SSL certs/keys
- default path to modules directory