* m4/gnulib-cache.m4: Use `dirfd'.
* libguile/filesys.c: Include Gnulib's <dirent.h> directly.
(dirfd): Remove. Suggested by Bruno Haible <bruno@clisp.org>.
This updates Gnulib to v0.0-4951-g6ff7b70.
* m4/gnulib-cache.m4: Add floor, ceil, frexp, and ldexp. Add wchar as
an explicit dependency; it had been present as an indirect dependency
before, but no longer. Remove round, which I had requested earlier,
but turned out to be unnecessary.