I just uploaded 0.5.3 to rubyforge.

This release fixes powerpc, cywin and FreeBSD installation/build
problems.  If none of those affect you, then there is no need to
upgrade from 0.5.1.

For those wondering, 0.5.2 was mostly Fedora fixes, so it was tagged
in the tree, but I didn't do a gem release for it, since I wanted to
roll in the cygwin and FreeBSD fixes.