* lib/cdefs.h (__inline, __restrict):
Copy from current glibc. This fixes glibc bug 17721,
which Gnulib had already fixed in a different way.
(__nonnull): Lessen the distance from glibc by using the
glibc definition inside an ‘#ifndef __nonnull’.
(__attribute_nonstring__): New macro, copied from
current glibc.
* lib/libc-config.h (__attribute_nonstring__): New undef.
(__restrict): Remove; workaround no longer needed.
Keep the __inline workaround, though, as it uses HAVE___INLINE to
support more compilers than the glibc __inline can.