Multi-precision division. Here be dragons.

Given u and v, where u is n+m digits, and v is n digits (with no leading zeros),
the goal is to return quo, rem such that u = quo*v + rem, where 0 ≤ rem < v.
That is, quo = ⌊u/v⌋ where ⌊x⌋ denotes the floor (truncation to integer) of x,
and rem = u - quo·v.


Long Division

Division in a computer proceeds the same as long division in elementary school,

	// Round to integer, float64 only.
	// Special cases:
	//   ±∞  → ±∞ (sign preserved)
	//   ±0  → ±0 (sign preserved)
	//   NaN → NaN
	{name: "Floor", argLength: 1},       // round arg0 toward -∞
	{name: "Ceil", argLength: 1},        // round arg0 toward +∞
	{name: "Trunc", argLength: 1},       // round arg0 toward 0

		{name: "FFLOOR", argLength: 1, reg: fp11, asm: "FRIM"},                                          // floor(arg0), float64
		{name: "FCEIL", argLength: 1, reg: fp11, asm: "FRIP"},                                           // ceil(arg0), float64