Please mark bison-2.7.1.ebuild stable.
Stable for PPC64.
amd64 stable
Stable for HPPA.
x86 stable
ppc stable
i've done the rest now: http://gitweb.gentoo.org/repo/gentoo.git/commit/?id=61610874bafcb780e1fd46f001abe3b0fcf92e01