build: Fix for Microsoft MSVC.

Authored by werner on Mon, Feb 4, 11:50 AM.

Description

build: Fix for Microsoft MSVC.

* src/gpgrt-int.h (_gpgrt_functions_w32_pollable): Declare with extern
so that strict toolchains don't get confused.
  • GnuPG-bug-id: T4356
  • Signed-off-by: Werner Koch <wk@gnupg.org>