grblHAL builds from Oct 2022 to April 2023 do not spin down the spindle (or laser) when stop command issued

[troth530]

Originally reported here https://github.com/grblHAL/Plugin_WebUI/issues/10

If stop command is issued by a streamer during streaming the spindle enable pin will disable, but the spindle will not spin down. In laser mode this leaves the laser turned on. After stopping the stream M5 will not spin down the spindle. A M4 followed by M5 will power down the spindle. This was verified in 3 senders including IOsender.

Build 1.1f20230501 partially fixed the issue and stopping the stream spins down the spindle, but spindle enable pin remains active. After stopping the stream, M4 issued by M5 will turn off the spindle enable pin. This is at least safer, but stopping a stream or M5 should be absolute and turn everything off.

Thank you!