maint: update gnulib for syntax-check on BSD

In particular, this incorporates Roman's patches to allow
'make syntax-check' to work on BSD with its exec argv
limitations that previously failed when trying to grep the
large number of files present in libvirt.

cfg.mk needs similar changes, but that will be tackled separately.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

bootstrap

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2018-10-13.05; # UTC
+scriptversion=2019-01-04.17; # UTC
 
 # Bootstrap this package from checked-out sources.
 
@@ -963,6 +963,16 @@ fi
 bootstrap_post_import_hook \
   || die "bootstrap_post_import_hook failed"
 
+# Don't proceed if there are uninitialized submodules.  In particular,
+# the next step will remove dangling links, which might be links into
+# uninitialized submodules.
+#
+# Uninitialized submodules are listed with an initial dash.
+if $use_git && git submodule | grep '^-' >/dev/null; then
+  die "some git submodules are not initialized. "     \
+      "Run 'git submodule init' and bootstrap again."
+fi
+
 # Remove any dangling symlink matching "*.m4" or "*.[ch]" in some
 # gnulib-populated directories.  Such .m4 files would cause aclocal to fail.
 # The following requires GNU find 4.2.3 or newer.  Considering the usual