Minimum bison requirement for building glibc/gettext

["Steve Ellcey " <sellcey at imgtec dot com>]

Sometime in the last couple of days I have noticed my glibc builds 
failing with:

/usr/bin/bison --yacc --name-prefix=__gettext --output plural.c plural.y
/usr/share/bison/yacc.c:94: error: invalid pure value: pure
/usr/share/bison/yacc.c:94: the top level
plural.y:46.9-16: invalid value for %define Boolean variable `api.pure'
make[2]: *** [plural.c] Error 1
make[2]: Leaving directory `/scratch/sellcey/repos/nightly2/src/glibc/intl'
make[1]: *** [intl/subdir_lib] Error 2
make[1]: Leaving directory `/scratch/sellcey/repos/nightly2/src/glibc'
make: *** [all] Error 2
Error: Make command failed, stopping build.

I haven't changed plural.y locally, I think the recent gettext merge just
caused my git checkout to create plural.y with a later timestamp then plural.c.

I am building on ubuntu 12.04 with bison 2.5.  Do I need to use a newer
bison?  It looks like the plural.c in the source tree was created by bison
2.7.  Is the required version documented somewhere?  I didn't see anything
in the glibc Wiki about the build requirements for glibc.

I can work around this by touching plural.c or updating the bison on my
build machines but I was wondering if there was a better way to handle
this.

Steve Ellcey
sellcey@imgtec.com