[Python-3000] Fix imghdr module for bytes

[Joel Bender]

Greg Ewing wrote:

> I'm wondering whether we want a "byte character literal"
> to go along with "byte string literals":
> 
>    h[0] == c"P"
> 
> After all, if it makes sense to write an array of bytes
> as though they were ASCII characters, it must make sense
> to write a single byte that way as well.

Would you propose these to be mutable as well?  Ugh.  :-)


Joel