* libtoolize.m4sh: Don't use func_serial_update as a copy

* libtoolize.m4sh: Don't use func_serial_update as a copy
function for libtool m4 files with no macro_regex.  If the
files are copied directly into aclocal.m4, because
AC_CONFIG_MACRO_DIR isn't set for example, there is no way
to tell what serial number goes with what source file.
(func_serial_update): For future-proofing, only make the second
serial number check if the destination file wasn't m4_included
into aclocal.m4 (and hence updated automatically by the cat of
copying a new version to the dest directory).