Expose bcf_fmt_sized_array in vcf.h

[arq5x]

Hi Heng,

I am working on a C++ interface to BCF2 that exposes bcf1_t structs through a C++ class. In order to do so, I need to mimic much of the logic currently in vcf_format1(). This function uses bcf_fmt_sized_array (and possibly other functions) that are not declared in vcf.h, which prevents mimicking the unwinding of the BCF record in my class.

Would you be willing to declare a prototype for this function in vcf.h?