[libxslt] Run Travis ASan tests with "sudo: required"

[Nick Wellnhofer <nwellnhof src gnome org>]

commit ffd2322a6953b3fc4c6e5a0e04f3b713c99e0ac1
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Tue Jul 24 02:20:14 2018 +0200

    Run Travis ASan tests with "sudo: required"
    
    See https://github.com/travis-ci/travis-ci/issues/9033

 .travis.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.travis.yml b/.travis.yml
index 8994be07..1a02fdef 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,5 @@
 language: c
-sudo: false
+sudo: required
 matrix:
   include:
     # Try to emulate a C89 compiler on a POSIX system by disabling as many