DIV/IDIV should trap on all overflow, not just divide by zero

[neldredge]

If IDIV would produce a quotient of 0x8000 (word) or 0x80 (byte), the real 8086 traps (INT 0, divide overflow). 8086-Emulator yields 0x8000 and continues. (Note this behavior changed between 8086 and 80386, not sure what the 80186/80286 did.)

[neldredge]

In fact the emulator only traps on div/idiv when the divisor is actually zero. It should trap whenever the mathematical result does not fit in the destination register. For instance

mov ax, 0xffff
mov dx, 0xffff
mov bx, 1
div bx

should trap with INT 0.

[YJDoc2]

Yes, this is correct. When implementing, apparently I read the spec incorrectly, and thought it was specifically for 0