missing instructions EXT and INS

[Dylan-Brotherston]

FAILED: EXT
  --> /dev/stdin:12:5
   |
12 |     EXT $t1, $t2, 2, 2
   |     ^^^^^^^^^^^^^^^^^^ unknown instruction `EXT`

FAILED: INS
  --> /dev/stdin:12:5
   |
12 |     INS $t1, $t2, 2, 2
   |     ^^^^^^^^^^^^^^^^^^ unknown instruction `INS`

[insou22]

Backburnered because size is mneant to be encoded in Rd which will make just about all of mipsy rather angry due to the fact it's not actually meant to be a register