Build roken using libtool

Previously it was version 1.1; just in case I did something terrible,
bump it to 2.0, as was done for the other libtool conversions.

Install both the libtool archive and the static archive to $(TOP_LIBDIR),
so that all our internal consumers can just use -L$(TOP_LIBDIR) -lrokenafs
(well, via the LDFLAGS_roken and LIB_roken aliases) whether linking
statically or shared.  Installing the libtool archive gets us the shared
library there, but we have to then remove the libtool archive, since
this is not the location we told libtool we would install to (the prefix
we configured with), and libtool would get confused trying to use this
installed, but installed-at-the-wrong-place libtool archive.

Add rk_vsyslog to the export list, for AIX.

It is tempting to eschew this installation and instead point LIB_roken
at the libtool archive file librokenafs.la directly (with empty
LDFLAGS_roken), but this is not possible until all consumers of roken
are converted to build using libtool.  In practice, this will probably
not happen until LWP is evicted from the tree.

Change-Id: If6ab6c2d57c0a1b1511f9631b9aeb522d7e7392b
Reviewed-on: http://gerrit.openafs.org/11477
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: D Brashear <shadow@your-file-system.com>