oggpackB_writeclear() uses different bit packing conventions for source and target buffers
bitwise.c:177:
if(bits)
w(b,(unsigned long)(ptr[bytes]),bits);
The above line assumes that the last (n%8) bits of the input buffer are always in
the least most significant bits of the last byte.
However, this means one cannot copy the bits from another oggpack_buffer written
to with oggpackB_write(), as it stores them in the most significant bits of the
last byte.
I.e., oggpackB_write(&opb1,oggpackB_get_buffer(&opb2),oggpackB_bits(&opb2))
fails in general.