Replace LT_INIT by AC_ macros in configure.ac

This change is asked by Barry Grumbine to fix build on OpenBSD

configure.ac

@@ -63,7 +63,8 @@ AC_PROG_CXX
 AC_LIBTOOL_WIN32_DLL
 AC_PROG_LIBTOOL
 AC_PROG_MAKE_SET
-LT_INIT([disable-static])
+AC_DISABLE_STATIC
+AC_PROG_LIBTOOL
 
 # Checks for header files.
 AC_HEADER_STDC