Only add trailing carriage return to messages if output is a raw tty.

If output is being written to a terminal in "raw" mode, we need to
add a carriage return after the newline to avoid "stair-step" output.
However, we should not write the carriage return if the terminal
is in "cooked" mode, output to a pipe, or output redirected to a file.
Bug #1042.

lib/util/fatal.c

@@ -239,7 +239,7 @@ warning(const char *errstr, const char *fmt, va_list ap)
             fputs(": ", stderr);
             fputs(errstr, stderr);
         }
-        if (isatty(fileno(stderr)))
+        if (sudo_term_is_raw(fileno(stderr)))
             putc('\r', stderr);
         putc('\n', stderr);
     }