Add bcf_format_gt_v2 function

Author: kojix2

lib/hts/libhts/vcf.rb

@@ -548,6 +548,11 @@ module LibHTS
       :bcf_float_missing,
       [],
       :uint32
+
+    attach_function \
+      :bcf_format_gt_v2,
+      [BcfHdr, BcfFmt, :int, KString],
+      :int
   end
 end