Add structured version info for dbm.ndbm

Feature or enhancement

dbm.ndbm can be built with GDBM's compatibility interface, with Berkeley DB, or with a classic NDBM library, and only exposes library, the name of the implementation. No version information is available, and library is 'GNU gdbm' even for a classic NDBM library, because the USE_NDBM build assumes GDBM.

The library used by dbm.ndbm may differ from the one used by dbm.gnu (different builds of GDBM, or Berkeley DB), so dbm.ndbm needs its own constants, named after the library it was built with:

• if library is 'GNU gdbm': GDBM_VERSION_INFO, gdbm_version_info and gdbm_version, as in dbm.gnu (gh-157478).
• if library is 'Berkeley DB': DB_VERSION and DB_VERSION_INFO for the build-time version (DB_VERSION_STRING, DB_VERSION_MAJOR/MINOR/PATCH), db_version and db_version_info for the runtime version (db_version()).
• for a classic NDBM library there is no version information; library should be 'ndbm'.

Linked PRs

• gh-157484

Beginne mit der Implementierung von dbm.ndbm und vergleiche die offengelegten Bibliotheksinformationen mit dbm.gnu, wie in gh-157478 beschrieben. Prüfe die Build-Zeit- und Laufzeit-Versionsanforderungen für GNU gdbm und Berkeley DB und verifiziere, dass klassisches NDBM keine Versionsinformationen meldet und sich als ndbm identifiziert; gh-157484 weist darauf hin, dass die Arbeiten daran bereits im Gange sind.