PNS v3.6 got renamed to V4

Because of historical reasons three different Profinet IO Device stack generations exist:

• /wiki/spaces/PNS3V5/pages/123211126
• V3.5
• V4

The generation V4 was formerly called V3.6. But to show that this is a completely new implementation and has nothing in common with the other stack generations it was decided to rename it from v3.6 to v4.
This change is just a version number issue, no functional enhancement or incompatible API change is done while updating the version number.