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

从 dbm.ndbm 的实现开始，并按照 gh-157478 中的参考，将其公开的库信息与 dbm.gnu 进行比较。检查 GNU gdbm 和 Berkeley DB 的构建时与运行时版本要求，并验证经典 NDBM 不报告版本信息且将自身标识为 ndbm；gh-157484 表明相关工作已经在进行中。