Move libxo to /lib

Update ObsoleteFiles to reflect libxo move.

Reviewed by: ngie
Differential Revision: https://reviews.freebsd.org/D1370


git-svn-id: svn+ssh://svn.freebsd.org/base/head@276195 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f