Enhancements:
- Import some of memory manager debug facilities from PostgreSQL. (Tatsuo Ishii)
- Use pg_get_expr() instead of pg_attrdef.adsrc to support for PostgreSQL 12. (Bo Peng)
- Enhance shutdown script of pgpool_setup. (Tatsuo Ishii)
    - Make shutdownall to wait for completion of shutdown of Pgpool-II.
    - If environment variable CHECK_TIME_WAIT is set to true, use netstat command to confirm usage of the TCP/IP port while executing shutdown script.
- Deal pgpool_adm extension with PostgreSQL 12. (Tatsuo Ishii)

Bug fixes:
- Fix pgpool_setup to produce correct follow master command. (Tatsuo Ishii)
- Fix query cache module so that it checks oid array's bound. (Tatsuo Ishii)
- Fix off-by-one error in query cache module. (Tatsuo Ishii)
- Fix segfault when samenet is specified in pool_hba.conf. (Tatsuo Ishii)
- Fix to deal with backslashes according to the config of standard_conforming_strings in native replication mode. (bug 467) (Bo Peng)
- Fix memory leaks. (Tatsuo Ishii)