Copy OpenSSL DLLs explicitly on Windows, rather than using fixup_bundle.

fixup_bundle was causing problems on Linux and didn't always find the right DLL on Windows.  It was also really slow on both platforms.

This commit just copies the two OpenSSL DLLs for each target that needs it.
Copy libssh2 DLL to example and test directories when building as a shared library.

Otherwise they won't work out-of-the-box.