linux-user: Report error message on stderr, rather than stdout

Code change produced with:

  git ls-files linux-user | \
  xargs sed -i -E 's/(\s+)printf\s*\(("Unhandled.*)\);/\1fprintf(stderr, \2);/g'

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20180706155127.7483-4-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/alpha/cpu_loop.c

@@ -196,7 +196,7 @@ void cpu_loop(CPUAlphaState *env)
             arch_interrupt = false;
             break;
         default:
-            printf ("Unhandled trap: 0x%x\n", trapnr);
+            fprintf(stderr, "Unhandled trap: 0x%x\n", trapnr);
             cpu_dump_state(cs, stderr, fprintf, 0);
             exit(EXIT_FAILURE);
         }