Use MOVED_LIBS for the libalias modules being moved to /lib.

This is a bit more unusual in that the modules dropped their major
version suffix at the same time, so the old files being removed by
MOVED_LIBS in this case are the symlinks to the old libraries.

Reviewed by: emaste
Sponsored by: The University of Cambridge, Google Inc.
Differential Revision: https://reviews.freebsd.org/D33849

(cherry picked from commit f033840b253ebb28eee25beafde4d6863f5f6e57)