DVDFab HD Decrypter expects that unused part of output buffer is not
modified.

winemac: Extract new function from macdrv_EnumClipboardFormats() parameterized by the target pasteboard.

winemac: Extract new function from macdrv_IsClipboardFormatAvailable() parameterized by the target pasteboard.

winemac: Extract new function from macdrv_GetClipboardData() parameterized by the target pasteboard.

... not just the general pasteboard (although the general pasteboard is
still the default).

Mac apps generally put TIFF on the pasteboard, but Windows programs are
more likely to handle CF_DIB or CF_BITMAP which map to BMP.