Quick and rough scan of genome for duplications
of segmental (between scaffolds), and
tandem (diagonal on same scaffold) types.
Note: Self-matches are removed (the true diagonal)
so that any near-diagonal lines are due to nearby duplications.
Courtesy of Megablast (NCBI), and DiagHunter by Steve Cannon,
who wrote it to find Arabidopsis segmental and tandem regions.