typedef struct LogicalDecodingContext

Hi,

During a recent code review, I noticed a lot of 'struct
LogicalDecodingContext' usage.

There are many function prototypes where the params are (for no
apparent reason to me) a mixture of structs and typedef structs.

AFAICT just by pre-declaring the typedef struct
LogicalDecodingContext, all of those 'struct LogicalDecodingContext'
can be culled, resulting in cleaner and more consistent function
signatures.

The PG Docs were similarly modified.

PSA patch for this.  It passes make check-world.

(I recognize this is potentially the tip of an iceberg. If this patch
is deemed OK, I can hunt down similar underuse of typedefs for other
structs)

Thoughts?

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Kind Regards,
Peter Smith.
Fujitsu Australia