Changes since beta1:
- Fix Lua 5.4 C API: correct version guards (== 502 → >= 502) across
  all hook functions (setup, screen, final, db)
- Fix Lua 5.4 C API: remove unguarded lua_load/lua_dump compat shims
- Fix Lua 5.4 C API: add missing strip argument to lua_dump call sites
- Fix Lua 5.4 C API: remove stale lua_pop() after luaL_newlib/lua_setglobal
- Fix signtable validation walk in dkimf_config_load(): missing KeyTable
  entries were not being caught due to datasplit OPTIONAL flag bug
- Port integration tests to CMake out-of-source build layout
- Fix miltertest: connect-failure returns nil instead of throwing
- Fix miltertest: add expect_exit option to startfilter for conf-check tests
- Disable integration tests for permanently removed features:
  t-lua-rbl, t-sign-atps, t-verify-ss-atps, t-verify-ss-rep,
  t-sign-ss-replace