* Misc fixes and improvements
- Get rid of most critical sections on the Serial port drivers for AVR and DUE. Proper usage of FIFOs should allow interrupts to stay enabled without harm to queuing and dequeuing.
Also, with 8-bit indices (for AVR) and up to 32-bit indices (for ARM), there is no need to protect reads and writes to those indices.
- Simplify the XON/XOFF logic quite a bit. Much cleaner now (both for AVR and ARM)
- Prevent a race condition (edge case) that could happen when estimating the proper value for the stepper timer (by reading it) and writing the calculated value for the time to the next ISR by disabling interrupts in those critical and small sections of the code - The problem could lead to lost steps.
- Fix dual endstops not properly homing bug (maybe).
* Set position immediately when possible
Also simplify logic on all ARM-based interrupts. Now, it is REQUIRED to properly configure interrupt priority. USART should have highest priority, followed by Stepper, and then all others.
* Merging early because of build failures. See #8105
* Make LPC1768 pinmapping not specific to Re-ARM
* Add HAL_PIN_TYPE and LPC1768 pin features
* M43 Updates
* Move pin map into pinsDebug_LPC1768.h
* Incorporate comments and M226
* Fix persistent store compilation issues
* Update pin features
* Update MKS SBASE pins
* Use native LPC1768 pin numbers in M42, M43, and M226
* Get UBL Mesh Generation, Mesh Save & Mesh Load working with 32-Bit platforms
* clean up read_data() and write_data() for non-LPC1768 HAL's
* Get read_data() and write_data() return codes consistent
All HAL's read_data() and write_data() return false if they succeed.
* Get read_data() and write_data() return codes to be consistent
Make read_data() and write_data() return true if an error happens.
* Say UBL is now checked out on machine types in default Configuration.h file.
