Enable optional static builds

* use LT_INIT instead of AC_PROG_RANLIB
* remove redundant libbsc entries

The default (for both manual and .deb builds) is to use shared build (as
before) - the static build is entirely optional.

Based on work by Sergey Kostanbaev <sergey.kostanbaev@gmail.com> and
Alexander Chemeris <Alexander.Chemeris@gmail.com>.

Change-Id: Ibcd1da98302413182c85e25c4cb7d69d9e38c35a
diff --git a/openbsc/configure.ac b/openbsc/configure.ac
index c6ae159..ff51ccf 100644
--- a/openbsc/configure.ac
+++ b/openbsc/configure.ac
@@ -16,7 +16,7 @@
 AC_PROG_MAKE_SET
 AC_PROG_CC
 AC_PROG_INSTALL
-AC_PROG_RANLIB
+LT_INIT
 
 dnl check for pkg-config (explained in detail in libosmocore/configure.ac)
 AC_PATH_PROG(PKG_CONFIG_INSTALLED, pkg-config, no)