bcftools view -G should remove FORMAT header lines

[winni2k]

Running bcftools view -G input.bcf drops all columns past the INFO column. However, the headers are not updated to reflect this change. I'll write a pull request for this, but I thought I'd put it here so I don't forget.

[mcshane]

Thanks Winni. Pull request would be welcome. There is some similar code in vcfannotate.c.

[winni2k]

I have submitted pull request #251 that fixes this issue.