Normalise [q[m-1],...,q[0]], yields q.
If m>=n>1, perform a multiple-precision division:
We have a/b < beta^(m-n+1).
- s:=intDsize-1-(hightest bit in b[n-1]), 0<=s<intDsize.
+ s:=intDsize-1-(highest bit in b[n-1]), 0<=s<intDsize.
Shift a and b left by s bits, copying them. r:=a.
r=[r[m],...,r[0]], b=[b[n-1],...,b[0]] with b[n-1]>=beta/2.
For j=m-n,...,0: {Here 0 <= r < b*beta^(j+1).}