While homing or probing it might be bad if the stop/trobe triggers during the first part and the second is still in the buffer.

-Report SERIAL_XON_XOFF in Extended Capabilites M115 report for hosts
-Remove outdated 256 size limitation from comments on RX_BUFFER_SIZE defines
config updates
-Update error checking conditions

Fix #8577

During long lasting moves of a delta machine neither the temperatures are maintained nor buttons checked nor ... .
The fix is to call 'manage_heater()' and 'idle()' every now and then in the loop where the move is segmented. 
The code is abot the same as in G2_G3 wher we had the same problem with too large circles lasting too long.
Fixing #7510

* Initialize mixing virtual tools to behave like standard a multi-extruder setup

* Update Marlin_main.cpp

* Update Marlin_main.cpp

Does it?

Implemented synchronization message output for NanoDLP printers (nanodlp.com).
If optional feature is enabled in `Configuration_adv.h`, Marlin will ouput "Z_move_comp" string to serial after completing any G0/G1 Z-axis movements. This feature patched on previous versions(1.0) is used by NanoDLP to synchronize Z-axis movement with projector exposure in DLP stereolithography printers.

Example Configuration.h files are not updated yet.   You need to cross
your settings over to the default Configuration.h file in the \Marlin
directory.   (UBL_G26_MESH_VALIDATION enablement has moved to a new
location in the file.)

For parity with bugfix-2.0.x

Just aligned with version 2.0. Here bug was not present

Followup to 13a3fb1acc

This PR will address two issues reported in #8492. Just one is left because I don't know if it is an issue or not

1) when no home is done ("no_move" is set) tool change should never move X & Y because... I don't know where I am...only Z should be adjusted to avoid bed collision if other nozzle is lower than current.
2) Since no move no bed level matrix should be applied
    When SWITCHING_NOZZLE is enabled and system is homed there are two movements to go to destination, but first can move Z to older position and then crash on the bed

* Fix up Travis CI and compile warnings/errors

* No ULTRA_LCD with REPRAP_DISCOUNT_SMART_CONTROLLER

* No point in setting all the endstop plugs

This fixes the old implementation of M428 which was broken, did not
match the website, and made no sense.

Thanks @RowanMeara!