A few of the T4 and now T4.1 Serial ports support a CTS pin.  One was previous fixed, added the others to tables.

Also T4.1 has Some Serial port pins in the area that the optional memory chips could be installed

Fixed the Serial2 object to use the new correct pins, plus made Serial8 only valid for T4 B1 (not B2).

Also I defined IO pins for the six signals associated with the SD Card slot.

I have tested these both as IO pins and now as SPI2

Add some support for serialEventX calls when yield is called.

Currently keep table of which SerialX objects are Used (.begin called) and each has their own function which does the
if (Serial1.available()) serialEvent1();

Calling SerialX.end(), removes the call from the list.  Also the default weak pointer serialEventX functions call the disable function, as to only be called once as no one is actually processing them...

At some point will integrate this with EventResponder

Hopefully will be able to get this such that only those objects that are used will be brought in by the system...