special handling for PKCS11 providers on win32

special handling for PKCS11 providers on win32

Change win32 dynamic loader behavior when supplying an absolute path.
The DLL location is considered/preferred to resolve dependencies.
Support in pkcs11-helper for loader flag is detected at compile time.

3rd party DLLs and additional dependencies do no longer need to be moved
to the OpenVPN directory or require changes to %PATH% configuration.

Signed-off-by: Marc Becker <marc.becker@astos.de>
Acked-by: Selva Nair <selva.nair@gmail.com>
Message-Id: <20221211200108.1402-1-marc.becker@astos.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25646.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit e299b8d0d62a4763b20bf9a3bd6aadf414aa89fe)