maint: update to latest gnulib
    
    Another update is required to pick up today's gnulib fix for mingw
    builds (now that gnulib turns on mingw's replacement printf that
    understands %lld, it must also tell the compiler to respect the
    improved definition of PRIdMAX and friends).
    
    * .gnulib: Update to latest.
    
    Signed-off-by: Eric Blake <eblake@redhat.com>