Bison 1.75 currently has the ~x86 keyword since it breaks xfree. I was searching the net and discovered that the problem is with xfree rather than bison, and that a patch was on the mailinglists at one point. The author hosts his patch here via cvsweb: http://www.jg555.com/cvs/cvsweb.cgi/~checkout~/patches/xfree/xfree-4.2.x.-bison.fixes.patch It doesn't look like portage applies this patch yet. If you read the patch, all it does is fix a handful of simple syntax errors, so I don't think we'll have to worry about it breaking anything. Was xfree the only thing holding up Bison 1.75?
Think pam as well, but I have a Redhat patch for that. Anyhow, patch added to -r2 of 4.2.1, thanks.
Updated xfree-4.2.1-r2, and pam-0.75-r10, thanks.