Need rundll32.exe command to set/remove RO flag

[loki890]

As "rundll32.exe shellbtrfs.dll,SendSubvol/RecvSubvol" works with RO volumes only and user works with RW ones And it should not offer to "send subvolume" on RW subvolume's context menu.

[ticpu]

Not offering the option at all might leave the user questioning why it is disabled or even missing, Btrfs is already quite complicated for new users, offering a dialog would be preferable IMO. It makes me think of when sendshots were approached to fix this problem directly. I'm surprised the RO option is settable via the properties tab and not rundll32, sounds like it might have been forgotten.