Because we were previously converting the bytes in the format
string into Rust's char type and then printing that using the
format machinery, byte values that were not valid single-byte
UTF-8 characters failed to print correctly.  I found this while
trying to implement qsort() because the output of my test program
was mysteriously incorrect despite it working when I used glibc.

Signed-off-by: Marat Safin <jeizsm@gmail.com>

* remove unnecessary cast

* add test and expected output