Add --dll-basename flag to give clients control over the DLL's base name. Split the...

Add --dll-basename flag to give clients control over the DLL's base name. Split the DLL installation makefile rules into digestible, platform-specific chunks. On Windows-side Unix-like environments, install the DLL into the bin dir. Requires testing and feedback from those platforms' package maintainers to confirm it follows the expectated conventions.

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