OpenBSD: fix device-hosted volume sizing

OpenBSD device length detection was returning the raw disk sector count from DIOCGPDINFO directly. That value is not bytes and it describes the physical/default disk label, which caused VeraCrypt to expose an incorrectly sized FUSE backing image through vnd for device-hosted volumes.

Use the current disklabel from DIOCGDINFO, derive the opened partition from the device minor number, and return the selected partition size in bytes. Keep the raw c partition on the whole-disk path by using DL_GETDSIZE there.

Also reject sector-misaligned device-hosted sizes during volume creation so new malformed OpenBSD device-hosted volumes are not created. Do not reject existing malformed headers at mount time, so users can still mount old OpenBSD-created volumes for recovery.

Refs #1589.

Refs #1593.

src/Core/VolumeCreator.cpp

@@ -282,6 +282,9 @@ namespace VeraCrypt
 				{
 					throw UnsupportedSectorSize (SRC_POS);
 				}
+
+				if (HostSize % options->SectorSize != 0)
+					throw ParameterIncorrect (SRC_POS);
 			}
 			else
 				options->SectorSize = TC_SECTOR_SIZE_FILE_HOSTED_VOLUME;