ESP32 ROM Table Support

[imwhocodes]

ESP32 already have CRC tables in the ROM blob https://github.com/espressif/esp-idf/blob/master/components/esp_rom/include/esp32/rom/crc.h

This is an initial commit to open the discussion for an ESP32 specialisation

I only implemented CRC32 (but not tested checksum mode, only CRC32)

Given the documentation all modes of CRC8 and CRC16 can be implemented

For the moment it is only a draft given:

1. Various CRC8 and CRC16 not implemented
2. Documentation say that you should bitwise negate (~) both the initial seed and the result, but I find out that it work (give same result as the library) only if I bitwise negate only the seed

[FrankBoesing]

That's very interesting! I'm currently moving house and will be looking at this next week or the week after.

[imwhocodes]

For the moment I disabled it on my codebase, I'm having problem where if I use the crc32 functions of the ROM the FreeRTOS start missing ticks, I'm supposing it is because being a ROM function it implicitly disable interrupts (even if there should be no need given what it do)

It need more testing and investigation for sure