Merge pull request percona#27 from dutow/pg1282

PG-1282: Fix `SELECT version()`

Updated pg_tde submodule reference

Stamp 15.1.

Stamp 14.6.

Stamp 13.9.

Stamp 12.13.

Stamp 11.18.

Stamp 10.23.

Doc: update release date for v15.

Drat, forgot this ...

Stamp 15rc2.