gnulib: update to fix location tracking in UTF-8 on Solaris

[Akim Demaille]

commit 85e83ea9687818cb4786d3e05b4419d68b792528
Author: Akim Demaille <address@hidden>
Date:   Wed May 8 09:18:17 2019 +0200

    gnulib: update to fix location tracking in UTF-8 on Solaris
    
    This update contains Bruno Haible's fix for the location tracking
    issue reported by Kiyoshi Kanazawa.
    
    https://lists.gnu.org/archive/html/bug-gnulib/2019-05/msg00020.html
    https://lists.gnu.org/archive/html/bug-bison/2019-04/msg00020.html

diff --git a/gnulib b/gnulib
index 14a92019..620857c4 160000
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 14a920195eee84550cfdd7a161896363d4796a22
+Subproject commit 620857c4dccb8f0548cdb855f6b2f46ebea3919e