C++ library and CLI tools for parsing and manipulating VCF files

[jwb]

Summary

C++ library and CLI tools for parsing and manipulating VCF files
Approved by jrm (mentor) or wen (mentor)
Differential to be added to commit message

Test Plan

portlint -AC: looks fine
Passed poudriere on {10.3,11.1}-{amd64,i386}
Tested in production as dependency of cutadapt bioinformatics software