Accept any libtool version

ct-ng will build its own version if a recent enough version is not
detected.

Signed-off-by: Alexey Neyman <stilor@att.net>

configure.ac

@@ -172,7 +172,7 @@ CTNG_PROG_VERSION_REQ_ANY([MAKE],
     [make_3_81_or_newer])
 
 # Check other companion tools that we may or may not build.
-CTNG_PROG_VERSION_REQ_STRICT([LIBTOOL],
+CTNG_PROG_VERSION([LIBTOOL],
     [GNU libtool >= 2.4],
     [libtool],
     [glibtool libtool],