Minimap2-2.20 (r1061)

This release fixed a bug in the Python module and improves the command-line
compatibiliity with v2.18. In v2.19, if -r is specified with an asm* preset,
users would get alignments more fragmented than v2.18. This could be an issue
for existing pipelines specifying -r. This release resolves this issue.

(2.20: 27 May 2021, r1061)