Updating to libtool 1.4.0.

* builds/unix/ltconfig: Removed.
* builds/unix/ltmain.sh, builds/unix/configure.in,
builds/unix/aclocal.m4: Updated.
* builds/unix/configure: Regenerated.
diff --git a/builds/unix/configure.in b/builds/unix/configure.in
index fc7547a..65f42c0 100644
--- a/builds/unix/configure.in
+++ b/builds/unix/configure.in
@@ -79,7 +79,7 @@
 
 AC_CHECK_FUNCS(memcpy memmove)
 
-AM_PROG_LIBTOOL
+AC_PROG_LIBTOOL
 
 dnl create the Unix-specific sub-Makefiles `builds/unix/unix-def.mk'
 dnl and 'builds/unix/unix-cc.mk' that will be used by the build system