3.9.1 Firmware for MK3S - M600 PATCH

This release is PATCHED for better handling of M600 with MMU2. See issue prusa3d#1363.
Built for MK3S with MMU2, English language ONLY.
Based on patch by @xiphmont: Allow selection of extruder in MMU Single mode at M600.
Patch was applied to original version tag 3.9.1 of MK3 branch.

3.9.1-RC1 Firmware for MK3S - M600 PATCH

This release is PATCHED for better handling of M600 with MMU2. See issue prusa3d#1363.
Built for MK3S with MMU2, English language ONLY.
Based on patch by @xiphmont: Allow selection of extruder in MMU Single mode at M600.
Patch was manually applied to original version tag 3.9.1-RC1 of MK3 branch.