/* Compare the memory regions S1 = [s1..s1+N1-1], S2 = [s2..s2+n2-1],
- alphabetically.
+ lexicographically.
This function's result is locale independent, unlike memcoll()'s.
Return a negative number if S1 < S2, a positive number if S1 > S2, or
0 if S1 and S2 have the same contents. */