Swap Mutex for Semaphore to manage multithreading.

[rominetb44]

Fixed assertion :
assertion "pbuf_free: p->ref > 0" failed: file "/home/runner/work/esp32-arduino-lib-builder/esp32-arduino-lib-builder/esp-idf/components/lwip/lwip/src/core/pbuf.c", line 765, function: pbuf_free

[MitchBradley]

You misspelled availablebuffer as availaiblebuffer. It is moot because the code in question has been rewritten entirely for FluidNC.

[rominetb44]

Hi

Thanks, I corrected it in my fork.
I gave more information here :
#1364