git commit 71f5e3f7b6 obviously wasn't tested on a big-endian host,
and the test fail message resulted in tcl errors.
* strings.c (unget_part_char): New function.
(print_strings): Use unget_part_char. Formatting.
* testsuite/binutils-all/strings.exp (test_multibyte): Don't
use square brackets in fail message. Expect "String1\nString2".