Crazy long VCF lines silently fail

[edawson]

Long vcf lines (such as those with the SV sequence in the ref/alt fields) silently fail parsing. This is standard get_line behavior but is a major issue.

Temporarily, I've fixed this by making the maximum line length really large. This is not an efficient solution. I need to think about how to write a better line-by-line or htslib-style parser (or just htslib) for variants.