Fix test for 32-bit machines

Current versions of Ubuntu LTS and Fedora will report i686 for the architecture, not i386, making this test fail on 32-bit machines
Merge pull request #56 from cottsay/x86-test-fix

Fix test for 32-bit machines
Use system encoding to read os version

Fedora 19 brought us the *wonderful* gift of special characters in the release name. Without specifying the encoding, the release file is read as ASCII (the Python 2 default) and can be wrong. We can use locale to detect the system's preferred encoding and read the file as such.

This problem prevents rosdep or any other ROS entity which uses this value from working correctly in Fedora 19.

locale.getpreferredencoding() was added in Python 2.3.