Bison fails to run because of vasnprintf() changes in macOS 10.13

[Jiří Techet]

Hello,

the vasnprintf() now intentionally crashes on macOS 10.13 when the
formatting string contains %n and is dynamically allocated, for more, see

http://lists.gnu.org/archive/html/bug-gnulib/2017-07/msg00056.html

The latest version of gnulib contains a fix for this; however the current
version of bison ships an older version of gnulib which makes bison crash
every time it's run. Please update to an up-to-date version of gnulib to
fix this issue on macOS 10.13.

Best regards,

Jiri