When building on 10.6 with a deployment target of 10.3 or 10.4,
various build errors occur, like:
    warning: 'struct winsize' declared inside parameter list
    error: 'struct rusage' has no member named 'ru_maxrss'

The problem is a test in configure.in that isn't prepared to handle
a two-digit Darwin kernel version: OS X 10.6 is Darwin 10.  The
patches backport the fix from trunk(2.7) to 2.6, 3.1, and py3k(3.2).
(As usual, autoconf needs to be run after applying to update configure.)