Optimize bigint division (div_rem::compute) for fast case

[ChALkeR]

Somewhere along

hermes/lib/Support/BigIntSupport.cpp

Lines 1797 to 1798 in 517e48e

	// If rhs has fewer digits than quoc/rem it must be resized.
	const bool needToResizeRhs = rhs.numDigits < resultSize;

If lhs.numDigits < rhs.numDigits, the result could be trivially optimized to [0, lhs]