gnulib: update for fix of fprintf-posix, which we'll use soon.

* etc/prefix-gnulib-mk (prefix): Adjust regex for make file
targets so that gnulib's new arg-nonnull.h and link-warning.h
are matched.
* gnulib: Update.

m4/.cvsignore

@@ -11,6 +11,8 @@ errno_h.m4
 error.m4
 exitfail.m4
 extensions.m4
+fcntl_h.m4
+fopen.m4
 getopt.m4
 getpagesize.m4
 gettext.m4
@@ -55,6 +57,7 @@ stddef_h.m4
 stdint.m4
 stdint_h.m4
 stdio-safer.m4
+stdio_h.m4
 stdlib_h.m4
 stpcpy.m4
 strerror.m4