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