Squashed 'htslib/' content from commit 5a0ee03

git-subtree-dir: htslib
git-subtree-split: 5a0ee032c4e94f5b2814c6f389278b404f439713
Merge commit '2d8feb4e7f87c4398bbfe587f9883f69dfbefed2' as 'htslib'