Debugger fixes

[cimarronm]

Fixes in debug disassembly and segment descriptor limits

What issue(s) does this PR address?

1. Fixes far direct jmp/call disassembly to use operand-size prefix instead of address-size prefix

Reference from DOS debug

A:\> debug test.com
-u 100
0827:0100 66EABC9A78563412  JMP     1234:56789ABC
0827:0108 0000              ADD     [BX+SI],AL
0827:010A 0000              ADD     [BX+SI],AL
0827:010C 0000              ADD     [BX+SI],AL
0827:010E 0000              ADD     [BX+SI],AL
0827:0110 0000              ADD     [BX+SI],AL
0827:0112 0000              ADD     [BX+SI],AL
0827:0114 0000              ADD     [BX+SI],AL
0827:0116 0000              ADD     [BX+SI],AL
0827:0118 0000              ADD     [BX+SI],AL
0827:011A 0000              ADD     [BX+SI],AL
0827:011C 0000              ADD     [BX+SI],AL
0827:011E 0000              ADD     [BX+SI],AL

dosbox's debugger

before fix

⎺⎺⎺⎺Code Overview⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺
0827:00000100 66EABC9A7856        jmp  5678:9ABC
0827:00000106 3412                xor  al,12
0827:00000108 0000                add  [bx+si],al             ds:[3378]=626F
0827:0000010A 0000                add  [bx+si],al             ds:[3378]=626F
...

after fix

⎺⎺⎺Code Overview⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺
0827:00000100 66EABC9A78563412    jmp  1234:56789ABC
0827:00000108 0000                add  [bx+si],al             ds:[3378]=626F
0827:0000010A 0000                add  [bx+si],al             ds:[3378]=626F
...

2. Fixes segment descriptor limits on expand-down segments

Does this PR introduce new feature(s)?

No

Does this PR introduce any breaking change(s)?

No