silk-hidapi-0.8.0-rc2: windows: Always open with sharing enabled

In the past, there was desire to make hid_open() open devices
exclusively, preventing devices from being opened more than once.
Unfortunately, recent versions of Windows have made this largely
impossible for many devices, as it appears that Windows itself is
holding certain HID devices open or preventing them from being
opened in exclusive mode.

This patch will always open devices in SHARED mode on Windows.