pgsql: Mark all symbols exported from extension libraries PGDLLEXPORT.

Mark all symbols exported from extension libraries PGDLLEXPORT.

This is in preparation for defaulting to -fvisibility=hidden in extensions,
instead of relying on all symbols in extensions to be exported.

This should have been committed before 089480c0770, but something in my commit
scripts went wrong.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20211101020311.av6hphdl6xbjbuif@alap3.anarazel.de

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/8cf64d35eaccab967c51d8bccf2c1babe3f84715

Modified Files
--------------
contrib/hstore/hstore.h                    | 16 ++++++------
contrib/ltree/ltree.h                      | 40 +++++++++++++++---------------
src/include/fmgr.h                         |  2 +-
src/pl/plpython/plpy_elog.h                | 10 ++++----
src/pl/plpython/plpy_typeio.h              | 36 +++++++++++++--------------
src/pl/plpython/plpy_util.h                |  8 +++---
src/test/modules/test_shm_mq/test_shm_mq.h |  2 +-
src/test/modules/worker_spi/worker_spi.c   |  2 +-
8 files changed, 58 insertions(+), 58 deletions(-)