* Make rz_buf_read consistent.
The IO buffer did not updated its seek after reading. Although most of the others do.
The behavior is now documented.
* Partially reverse seek on read for IO_FD and FILE buffers. Because it breaks too many tests.
* Add type when initializing RzBuffer.
* Remove duplicate documentation of RzBuffer read()
This adds an RzBuffer implementation that binds against RzIO's
rz_io_read_at/rz_io_write_at in order to access the mapped memory. This
is in contrast to the previous io RzBuffer, which has been renamed to
..._io_fd and which reads directly from a single file descriptor without
mapping.
To keep bf working, bin_bf now maps an area of zeroes because
otherwise the initial memory contents in RzIL would read as 0xff.
