Split ECPGdo() in constituent parts

This splits ECPGdo() into ecpg_prologue(), ecpg_do() and
ecpg_epilogue(), and renames free_params() into ecpg_free_params() and
exports it.  This makes it possible for future code to use these
routines for their own purposes.

There is no user-visible functionality change here, only code
reorganization.

Zoltán Böszörményi

Reviewed by Antonin Houska.  Larger, older versions of this patch were
reviewed by Noah Misch and Michael Meskes.
Add display of oprcode (the underlying function's name) to psql's \do+.

The + modifier of \do didn't use to do anything, but now it adds an oprcode
column.  This is useful both as an additional form of documentation of what
the operator does, and to save a step when finding out properties of the
underlying function.

Marko Tiikkaja, reviewed by Rushabh Lathia, adjusted a bit by me
Split ecpg_execute() in constituent parts

Split the rather long ecpg_execute() function into ecpg_build_params(),
ecpg_autostart_transaction(), a smaller ecpg_execute() and
ecpg_process_output().  There is no user-visible change here, only code
reorganization to support future patches.

Author: Zoltán Böszörményi

Reviewed by Antonin Houska.  Larger, older versions of this patch were
reviewed by Noah Misch and Michael Meskes.
Fix Hot Standby feedback sending when streaming busily.

Commit 6f60fdd7015b032bf49273c99f80913d57eac284 accidentally removed a
call to XLogWalRcvSendHSFeedback() after flushing received WAL to disk.
The consequence is that when walsender is busy streaming WAL, it doesn't
send HS feedback messages. One is sent if nothing is received from the
master for 100ms, but if there's a steady stream of WAL, it never happens.

Backpatch to 9.3.

Andres Freund and Amit Kapila
docs:  update PL/pgSQL docs about the use of := and =
doc: fix := description typo.
doc:  rename "Equals" to "Equal"
Prevent integer overflow with --progress >= 2148

If --progress=2148 or higher was given, the calculation of the next time
to report overflowed, and pgbench would print a progress report very
frequently.

Kingter Wang