gnulib: update to use its bitsets

Bison's bitset were moved to gnulib.

* lib/abitset.c, lib/abitset.h, lib/bbitset.h, lib/bitset.c,
* lib/bitset.h, lib/ebitset.c, lib/ebitset.h, lib/lbitset.c,
* lib/bitset_stats.c, lib/bitset_stats.h, lib/bitsetv-print.c,
* lib/bitsetv-print.h, lib/bitsetv.c, lib/bitsetv.h,
* lib/lbitset.h, lib/vbitset.c, lib/vbitset.h:
Remove.

* gnulib: Update.
* bootstrap.conf, lib/local.mk: Adjust.

bootstrap.conf

@@ -18,6 +18,7 @@
 # gnulib modules used by this package.
 gnulib_modules='
   argmatch assert
+  bitsetv
   calloc-posix close closeout config-h c-strcase
   configmake
   dirname