gnulib: update

Contains the creation of the xhash module.
https://lists.gnu.org/archive/html/bug-gnulib/2019-09/msg00046.html

* src/muscle-tab.c, src/state.c, src/symtab.c, src/uniqstr.c:
Use hash_xinitialize.

bootstrap.conf

@@ -25,7 +25,7 @@ gnulib_modules='
   error extensions fdl fopen-safer
   getopt-gnu
   gettext-h git-version-gen gitlog-to-changelog
-  gpl-3.0 hash inttypes isnan javacomp-script
+  gpl-3.0 inttypes isnan javacomp-script
   javaexec-script
   ldexpl
   libtextstyle-optional
@@ -48,6 +48,7 @@ gnulib_modules='
   xalloc
   xalloc-die
   xconcat-filename
+  xhash
   xlist
   xmemdup0
   xstrndup