Add Mavericks support to readline

This is a pre-emptive patch to readline to support Mac OS X 10.9 aka
Mavericks aka darwin13. The bug has been submitted to readline.

While patch 002 extended support from darwin10 to darwin12, this commit
modifies the patch to allow all versions of Darwin. The original patch
would have allowed all versions of Darwin after 8.0, which corresponds
with Mac OS X 10.4 aka Tiger. Surely no-one will be trying to install
this package on a PowerPC Mac running Panther or earlier? :-)
Prepare for release 6.2.4.2

Update the changelog and version number. This is a bugfix release to allow
building on Mac OS 10.9.