Merge remote-tracking branch 'remotes/elmarco/tags/slirp-pull-request' into staging

slirp: update to latest stable-4.2 branch

# gpg: Signature made Tue 28 Jul 2020 15:30:09 BST
# gpg:                using RSA key 87A9BD933F87C606D276F62DDAE8E10975969CE5
# gpg:                issuer "marcandre.lureau@redhat.com"
# gpg: Good signature from "Marc-André Lureau <marcandre.lureau@redhat.com>" [full]
# gpg:                 aka "Marc-André Lureau <marcandre.lureau@gmail.com>" [full]
# Primary key fingerprint: 87A9 BD93 3F87 C606 D276  F62D DAE8 E109 7596 9CE5

* remotes/elmarco/tags/slirp-pull-request:
  slirp: update to latest stable-4.2 branch
  test-char: abort on serial test error
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

slirp @ ce94eba2

-Subproject commit 2faae0f778f818fadc873308f983289df697eb93
+Subproject commit ce94eba2042d52a0ba3d9e252ebce86715e94275

tests/test-char.c

@@ -1200,7 +1200,7 @@ static void char_serial_test(void)
 
     /* test tty alias */
     qemu_opt_set(opts, "backend", "tty", &error_abort);
-    chr = qemu_chr_new_from_opts(opts, NULL, NULL);
+    chr = qemu_chr_new_from_opts(opts, NULL, &error_abort);
     g_assert_nonnull(chr);
     object_unparent(OBJECT(chr));