Zabbix

....I..... [ZBX-22307] restored dbschema building on OpenBSD

Due to some naive constructs in Makefile templates, building dbschemas
(or anything else, really) was broken on OpenBSD, as the generated
Makefile fragments were not valid and not accepted by OpenBSD's make,
resulting in compleat breakage of building from source.

These changes fix that by restructuring the database snippet directories
and reworking the generating of some of the patches.

Fixed a conflict in database/sqlite3/Makefile.am automake template,
where commit 93d2864069199b487456b810fb236df45f693341
("[DEV-4007] removed useless images.sql and data.sql for SQLite3 backend")
removed the targets for generating data.sql and images.sql.