pgsql: Add PGDLLEXPORTS to some plpgsql function declarations

Add PGDLLEXPORTS to some plpgsql function declarations

After -fvisibility=hidden was added by 089480c07705, plpgsql_check no
longer works; this quick hack fixes it.  It would be better to
restructure the plpgsql.h header so that this doesn't look as random,
but we can leave that for another day.

Reported-by: Pavel Stehule
Discussion: https://postgr.es/m/CAFj8pRAFxc3-SHMD3URU09JZXEKY3W-RwXKp8xPEnEq8rrka7w@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1caf915ff31e91031f0a0b8e1016df2b59d6f9de

Modified Files
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src/pl/plpgsql/src/plpgsql.h | 30 +++++++++++++++---------------
1 file changed, 15 insertions(+), 15 deletions(-)