Add support for PG15.

+ Fix backend crash on insert nonhasable record (Issue #38)

v.1.2.3

+ fix tests on SolarisOS (issue #33)
+ fix error on insert from table (issue #32)

v1.2.2

+ Add support for PG13 and PG14.
+ Fix remove_variable bug (Issue #27)
+ Fix "hash leak search" warning (without cursors)

- Added Postgres 12 support

- Bug fixes
- Added pgv_set() and pgv_get() arguments description (Issue #26)

All credits to @za-arthur and @CherkashinSergey

Optimize objects removal in subtransaction rollback

Remove unnecessary row notes from examples

#5 untroduce pgv_set() and pgv_get() functions to handle anynonarray …

…pseudotype