Adjust recognize-shared-libraries regex to avoid matching symlinks to

Adjust recognize-shared-libraries regex to avoid matching symlinks to
shared libraries.

This fixes a problem which resulted in 6.x->7.x upgrades having the
/usr/lib/libpthread.so -> libthr.so symlink missing; what happened was
that the old libpthread.so symlink pointed to /lib/libpthread.so.2 --
which matched the "/lib/*\.so\.[0-9]+" regex -- but the new symlink
didn't, so FreeBSD Update got confused and deleted the symlink as part
of its "remove old shared libraries" step.

To recreate the symlink (which I understand is necessary for ports like
KDE to build) on a 7.x system which FreeBSD Update upgraded from 6.x:
# ln -s libthr.so /usr/lib/libpthread.so

Reported by:	Dmitry RCL Rekman
Help diagnosing bug from:	kris
MFC after:	7 days