Internal auxiliary functions
This is an internal module.
A specialisation of Array.blit for int arrays.
(Performance reasons.)
int_series src srcpos dst dstpos len n:
Computes for every i, 0 <= i < len:
dst.(dstpos+i) = n + SUM(j=0..(i-1): src.(srcpos+j))
It is expected that src == dst implies srcpos >= dstpos.