merging some features from plpgsql2 project

failed: regress/enum, regress/strings, regress/numerology, regress/point, regress/lseg, regress/line, regress/box, regress/path, regress/polygon, regress/circle, regress/date, regress/time, regress/timetz, regress/timestamp, regress/timestamptz, regress/interval, regress/abstime, regress/reltime, regress/tinterval, regress/inet, regress/macaddr, regress/tstypes, regress/comments, regress/geometry, regress/horology, regress/regex, regress/oidjoins, regress/type_sanity, regress/opr_sanity, regress/copydml, regress/create_misc, regress/create_operator, regress/create_index, regress/create_view, regress/create_aggregate, regress/create_function_3, regress/create_cast, regress/constraints, regress/triggers, regress/inherit, regress/create_table_like, regress/typed_table, regress/vacuum, regress/drop_if_exists, regress/updatable_views, regress/rolenames, regress/roleattributes, regress/create_am, regress/sanity_check, regress/select, regress/select_into, regress/subselect, regress/union, regress/case, regress/join, regress/aggregates, regress/transactions, regress/portals, regress/arrays, regress/hash_index, regress/prepared_xacts, regress/brin, regress/gin, regress/gist, regress/spgist, regress/privileges, regress/init_privs, regress/security_label, regress/collate, regress/matview, regress/lock, regress/replica_identity, regress/rowsecurity, regress/object_address, regress/tablesample, regress/groupingsets, regress/drop_operator, regress/misc, regress/psql, regress/rules, regress/psql_crosstab, regress/amutils, regress/select_parallel, regress/select_views, regress/portals_p2, regress/foreign_key, regress/cluster, regress/dependency, regress/guc, regress/bitmapops, regress/combocid, regress/tsearch, regress/tsdicts, regress/foreign_data, regress/window, regress/xmlmap, regress/functional_deps, regress/advisory_lock, regress/json, regress/jsonb, regress/json_encoding, regress/indirect_toast, regress/equivclass, regress/plancache, regress/limit, regress/plpgsql, regress/copy2, regress/rangefuncs, regress/alter_table, regress/polymorphism, regress/rowtypes, regress/largeobject, regress/with, regress/event_trigger, regress/stats, regress/ri-trigger, regress/partial-index, regress/two-ids, regress/multiple-row-versions, regress/index-only-scan, regress/deadlock-simple, regress/deadlock-hard, regress/deadlock-soft, regress/deadlock-soft-2, regress/fk-contention, regress/fk-deadlock, regress/fk-deadlock2, regress/eval-plan-qual, regress/lock-update-delete, regress/lock-update-traversal, regress/insert-conflict-do-nothing, regress/insert-conflict-do-nothing-2, regress/insert-conflict-do-update, regress/insert-conflict-do-update-2, regress/insert-conflict-do-update-3, regress/insert-conflict-toast, regress/delete-abort-savept, regress/delete-abort-savept-2, regress/aborted-keyrevoke, regress/multixact-no-deadlock, regress/multixact-no-forget, regress/lock-committed-update, regress/lock-committed-keyupdate, regress/update-locked-tuple, regress/propagate-lock-delete, regress/tuplelock-conflict, regress/tuplelock-update, regress/nowait, regress/nowait-2, regress/nowait-3, regress/nowait-4, regress/nowait-5, regress/skip-locked, regress/skip-locked-2, regress/skip-locked-3, regress/skip-locked-4, regress/drop-index-concurrently-1, regress/alter-table-1, regress/alter-table-2, regress/alter-table-3, regress/create-trigger, regress/async-notify, regress/timeouts, regress/dblink, regress/money, regress/rangetypes, regress/pg_lsn, regress/select_distinct, tap/002_pg_dump, regress/alter_generic, regress/alter_operator, regress/async, regress/dbsize, regress/misc_functions, regress/tsrf, regress/temp, regress/domain, regress/prepare, regress/without_oid, regress/conversion, regress/truncate, regress/sequence, regress/returning, regress/xml