Like what was added for T3.x with that 3 yeard PR, I added the same support to T4.x

Added the PORT TOGGLE defines.  I copied the _PORTSET blocks and then simply used block editing in Sublime text to then change the SET to Toggle.

Also added in the code...

Test sketch:
```
void setup() {
  pinMode(13, OUTPUT);
}

int led = 13;
void loop() {
  digitalToggleFast(led);
  delay(500);
  digitalToggleFast(13);
  delay(250);
  digitalToggle(13);
  delay(1000);
  digitalToggle(led);
  delay(250);
}
```
Also added values to keywords.txt

This can be adjusted easyly by editing maxSpeed and maxSpeedBeforeDelay

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