Implement ADCR instruction

[craigthomas]

Implement the ADCR 6309 instruction mnemonic in the assembler. Adds contents of a source register, plus the carry flag, to the contents of the destination register. All registers except for Q and MD are allowed.

Immediate - $1031, 3 bytes

The command works with the following syntax:

ADCR r0,r1

Where r0 is the source and r1 is the destination. The source is stored as the high nibble of the operand byte, and the destination is stored as the low nibble of the operand byte. Valid source and destination values are:

0000 - D
0001 - X
0010 - Y
0011 - U
0100 - S
0101 - PC
0110 - W
0111 - V
1000 - A
1001 - B
1010 - CC
1011 - DP
1110 - E
1111 - F

Example:

$10 31 8E     ADCR A,E