[with patch, positive review] Fix readline build on FreeBSD

Imported from <a href="http://trac.sagemath.org/sage_trac/ticket/5874">trac #5874</a>.



Reported by: pjeremy

Component: FreeBSD

CC: chet.ramey@case.edu

Report Upstream: 

Authors: Peter Jeremy

Dependencies: 

Work issues: 

Reviewers: Mike Hansen

Merged in: sage-4.1.rc0

Attachments: <ol><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/5874/readline-5.2.p6.patch">readline-5.2.p6.patch: </a> by pjeremy at 20090423T08:48:23</li></ol>