No C{Get,Set}High support.

[PeterRugg]

Found by TestRIG. This is a feature added recently to ISAv9, and should be easy to add.

# 
#>QCVENGINE_TEST_V2.0
.4byte 0xff7208db # cgethigh x17, x4
#      Trap: False, PCWD: 0x0000000080000004, RD: 17, RWD: 0x00000000fff00000, I: 0x00000000ff7208db PRV_M XL:32 (cgethigh x17, x4)
# ╷
# │ ^ A, B v: mismatch in field trap: 0 != 1, mismatch in field rd_addr: 17 != 0, mismatch in field rd_wdata: 0xfff00000 != 0x0, mismatch in field pc_wdata: 0x80000004 != 0x0, mismatch in field mem_rdata: 
# ╵
#      Trap:  True, PCWD: 0x0000000000000000, RD: 00, RWD: 0x0000000000000000, MA: 0x0000000000000000, MWD: 0x0000000000000000, MWM: 0b00000000, MRD: 0x0000000000000000, MRM: 0b00001111 I: 0x00000000ff7208db PRV_? XL:? (cgethigh x17, x4)

# Test end
#      halt token