dlopen() is in SUSv2 and all targeted Unix systems have it. We still
need replacement functions for Windows, but we don't need a configure
probe for that.
Since it's no longer needed by other operating systems, rename dlopen.c
to win32dlopen.c and move the declarations into win32_port.h.
Likewise, the macros RTLD_NOW and RTLD_GLOBAL now only need to be
defined on Windows, since all targeted Unix systems have 'em.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
Thomas Munro