pgsql: Revert 0f5ca02f53

Revert 0f5ca02f53

0f5ca02f53 introduces 3 new keywords. It appears to be too much for relatively
small feature. Given now we past feature freeze, it's already late for
discussion of the new syntax. So, revert.

Discussion: https://postgr.es/m/28209.1586294824%40sss.pgh.pa.us

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/1aac32df89eb19949050f6f27c268122833ad036

Modified Files
--------------
doc/src/sgml/ref/begin.sgml | 17 +-
doc/src/sgml/ref/start_transaction.sgml | 17 +-
src/backend/access/transam/xlog.c | 13 --
src/backend/commands/Makefile | 3 +-
src/backend/commands/wait.c | 295 --------------------------------
src/backend/nodes/copyfuncs.c | 15 --
src/backend/nodes/equalfuncs.c | 13 --
src/backend/nodes/outfuncs.c | 28 ---
src/backend/parser/gram.y | 37 +---
src/backend/storage/ipc/ipci.c | 7 -
src/backend/storage/lmgr/proc.c | 4 -
src/backend/tcop/utility.c | 13 --
src/backend/utils/adt/misc.c | 2 +
src/include/commands/wait.h | 26 ---
src/include/nodes/nodes.h | 1 -
src/include/nodes/parsenodes.h | 12 --
src/include/parser/kwlist.h | 3 -
src/include/utils/timestamp.h | 2 -
src/test/recovery/t/020_begin_wait.pl | 85 ---------
src/tools/pgindent/typedefs.list | 2 -
20 files changed, 10 insertions(+), 585 deletions(-)