Ensure indirect function calls have the correct type.

[daviesrob]

Some HTSlib interfaces (notably kgetline(), kgetline2(), hts_itr_querys() and hts_parse_region()) have function callbacks that are intended to be generic, so the function signatures include a void * for data to be passed in. E.g. for kgetline() this would be the FILE * or hFILE * to read. Historically they have often been called with a function that has an explicit type (e.g. FILE * for fgets() used with kgetline) on the assumption that casting it to void * is harmless. Unfortunately doing this is strictly undefined behaviour and will fail in some conditions - for example if compiling with control flow integrity turned on. Recent versions of clang will also call this out when using undefined behaviour sanitizer. The solution is to create wrapper functions that do take a void *, and call the intended function with suitable casts.

Some new interfaces are also added so that the messy implementation details can be hidden away, and the inputs can be better type checked. Hopefully this should also allow the wrapper functions to be inlined away.

• hget_kstr() to read lines from an hFILE * to a kstring.

• kgetline() to read lines from a FILE * to a kstring.

• tbx_itr_querys1() to create a tabix iterator on a region. Used to reimplement the existing tbx_itr_querys() macro.

• bcf_itr_querys1() to create a region iterator an a bcf file Used to reimplement the existing bcf_itr_querys() macro.