cmd: Convert to using libtool

cmd: Convert to using libtool

Convert the libcmd and libcmd_pic libaries to being built using
libtool. Historically, these have been built as LWP code, but they
have no LWP dependencies, and no LWP-specific code within them. So,
make cmd a pthread-only library.

In addition to the libtool library liboafs_cmd.la, we build the
legacy libcmd.a and libcmd_pic.a as convenience libraries. libcmd64.a
(a 64bit variant, used solely by kdump), remains built through
"normal" means.

Update pthreaded users of libcmd to use the new liboafs_cmd.la. For
now, non-pthreaded users are left alone.

Change-Id: Id8445949754d1942f6e8752ae182b4e6f86fe94f
Reviewed-on: http://gerrit.openafs.org/8055
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>