docs for insert-file-contents use 'bytes'

[Ted Zlatanov <tzz@lifelogs.com>]

The docs for insert-file-contents say the range is in bytes, but that
function does decoding of the contents.  Can it, therefore, read from an
undesirable position (e.g. the middle of a UTF-8 sequence)?  How does
Emacs handle that?  Or does "bytes" really mean position by character?

Either way the docs need to state the operation mode clearly.  I'd do it
but I don't know enough :)

Thanks
Ted