bison?

[John Cremona <john.cremona@gmail.com>]

When did bison become a prerequisite for building pari?  I see that it
now is (in the svn development version).  It's not a problem for me
personally since I only use Linux and bison is standard, but it has an
effect on Sage (which does not have bison as a prerequisite).   Are
there alternatives?

John