Zabbix

...G...... [ZBX-13730] more changes in zbxregexp iface & impl

Using ZBX_REGEXP_* macros, defined in zbxregexp.h, to return
zbx_regexp procedure statuses.
Changed some zbxregexp function signatures.

Fixed some errors added in the previous commit.

Adding "runaway expression" as a cause for item failure.

Work in progress.
Needs integration with remaining items & extensive testing.