Explicitly include string.h to avoid warnings under MacOS X/clang
about implicit declarations of strerror() and strlen().
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>