Define EXEC_BACKEND in pg_config_manual.h
It was for unclear reasons defined in a separate location, which makes
it more cumbersome to override for testing, and it also did not have
any prominent documentation. Move to pg_config_manual.h, where
similar things are already collected.
The previous definition on the command-line had the effect of defining
it to the value 1, but now that we don't need that anymore we just
define it to empty, to simplify manual editing a bit.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/
b7053ba8-b008-5335-31de-
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