Add libtool support.

libzebra and libospfapiclient are now built shared, and linked shared
with the daemons.  This reduces the memory needed when running
multiple daemons; each daemon is at least 150k smaller.  Static
libraries are still built, and libtool should use them on platforms
which don't have shared libaries.  As with autoconf, the user of a
distribution does not need libtool; one just needs that to build from
CVS.

libospf.a is still a non-shared library, and still installed, not
because that makese sense, but because I don't understand why it is
the way it is now.

Note that the tree was tagged 'libtool-before' just before this commit.
diff --git a/zebra/main.c b/zebra/main.c
index 1083ae5..6d40d70 100644
--- a/zebra/main.c
+++ b/zebra/main.c
@@ -48,6 +48,9 @@
 pid_t old_pid;
 pid_t pid;
 
+/* Pacify zclient.o in libzebra, which expects this variable. */
+struct thread_master *master;
+
 /* Route retain mode flag. */
 int retain_mode = 0;