pgsql: Allow specifying pg_waldump --rmgr option multiple times.

Allow specifying pg_waldump --rmgr option multiple times.

Before, if you specified multiple --rmgr options, only the last one took
effect. It seems more sensible to select all the specified resource
managers.

Reviewed-By: Daniel Gustafsson, Julien Rouhaud
Discussion: https://www.postgresql.org/message-id/98344bc2-e222-02ad-a75b-81ffc614c155%40iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c8bf5098cbc4f32ca724d830d45d5ceb2ad7f96d

Modified Files
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doc/src/sgml/ref/pg_waldump.sgml |  3 ++-
src/bin/pg_waldump/pg_waldump.c  | 16 +++++++++-------
2 files changed, 11 insertions(+), 8 deletions(-)