reader: explicit casts for read_num_samples and first_sample_offset for vs8
reader: explicit casts for read_num_samples and first_sample_offset for vs8

xunchangguo/BMX,stuarthicks/bmx,ebu/ebu-bmx,Limecraft/ebu-bmx,kierank/bmxlib-bmx,kierank/bmxlib-bmx,xunchangguo/BMX,Limecraft/ebu-bmx,ebu/ebu-bmx,Limecraft/ebu-bmx,stuarthicks/bmx,xunchangguo/BMX,kierank/bmxlib-bmx,stuarthicks/bmx,ebu/ebu-bmx