Windows: Fix DND on non-parented windows (bugfix)

[AlexCharlton]

Hi Rustaudio, I'm opening up a slew of PRs so I figured I'd provide a small preamble for this first one. I had forked baseview years ago and quickly diverged enough that I never wound up trying to submit anything upstream. With the 0.1 release I finally decided get on board and contribute back.

The majority of these are relatively small bugfixes for Windows, though a few are new features – The PR descriptions will indicate what the contents contain.

Thanks in advance for the reviews!

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Filtering GetMessageW to hwnd precludes getting events from the OLE thread that's handling the DND. In practice this means that when dragging something into the baseview window, the drag process (that OLE thread) freezes up, making it impossible to complete the drag.

[prokopyl]

Hi! And thanks for submitting your changes, it is much appreciated!

Your PRs have quite a variety of changes between bug fixes, new features, platform support, some breaking changes and other improvements, so I'm going to order them according to our short-term roadmap, and then review them in that priority order.

That means I'm likely gonna make a few minor releases before I'll get to your bigger PRs. 🙂

[AlexCharlton]

Your PRs have quite a variety of changes between bug fixes, new features, platform support, some breaking changes and other improvements, so I'm going to order them according to our short-term roadmap, and then review them in that priority order.

Thanks for reviewing, @prokopyl! This makes sense to me!

[prokopyl]

Tested and looks good to me now! Thank you!