pgsql: pgoutput: Raise an error for missing protocol version parameter.

pgoutput: Raise an error for missing protocol version parameter.

Currently, we give a misleading error if the user omits to pass the
required parameter 'proto_version' in SQL API
pg_logical_slot_get_changes() or during START_REPLICATION protocol
message. The error raised is as follows which indicates that the wrong
version is passed.
ERROR:  client sent proto_version=0 but server only supports protocol 1 or higher

Author: Emre Hasegeli
Reviewed-by: Peter Smith, Amit Kapila
Discussion: https://postgr.es/m/CAE2gYzwdwtUbs-tPSV-QBwgTubiyGD2ZGsSnAVsDfAGGLDrGOA@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/c8bc807cf8bc741c83bc74553326856affee5a4f

Modified Files
--------------
src/backend/replication/pgoutput/pgoutput.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)