Update Configuration_adv.h

[jledgett]

Enable HOST_ACTION_COMMANDS support for people who use Octoprint.

[747lulu747]

This repository is based on the Marlin firmware, but with some changes. Such as starting and stopping work. HOST ACTION COMMANDS has an effect on starting and suspending work, we need some tests.

[evilC]

@jledgett have you actually built and flashed this? If so, was the custom flash process relatively painless? Have you tried flashing back to a stock firmware after?

[diogos88]

Any news on this request?

[Wombleyy]

I previously tried to activate host action commands as shown in this pull request. Though I did not think to enable host pause M76. I found numerous other issues (filament runout detection, M600 execution, power loss recovery, fast tool changes) attempting to serve prints from an OctoPrint host that needed further modification for smooth operation. Some I was able to address but ultimately abandoned it.

Unless @jledgett or others can confirm the host pause addition is sufficient (?), I believe the proposed commit would enable some functionality while introducing issues in likely scenarios.

@jledgett can you confirm runout, M600, power loss recovery, fast tool changes, etc, are smooth after this change?