[libxslt] Run Travis ASan tests under Xenial

[Nick Wellnhofer <nwellnhof src gnome org>]

commit e67e0afbdd4987c091eb4e3879f67f3ae002b987
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Mon Jun 3 14:56:24 2019 +0200

    Run Travis ASan tests under Xenial

 .travis.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.travis.yml b/.travis.yml
index f1e589eb..8d10d234 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,7 +10,7 @@ matrix:
            CFLAGS="-O2 -std=c89 -D_POSIX_C_SOURCE=200112L -Werror -Wno-error=array-bounds"
     # clang with AddressSanitizer and UndefinedBehaviorSanitizer.
     - compiler: clang
-      dist: trusty
+      dist: xenial
       env: CONFIG="--without-python"
            CFLAGS="-O2 -g -fno-omit-frame-pointer -fsanitize=address,undefined -fno-sanitize-recover=all 
-Werror -Wno-error=cast-align"
            UBSAN_OPTIONS=print_stacktrace=1