Ignore additional generated files:

        aclocal-fallback/libtool.m4
        aclocal-fallback/ltoptions.m4
        aclocal-fallback/ltsugar.m4
        aclocal-fallback/ltversion.m4
        aclocal-fallback/lt~obsolete.m4

Change-Id: I7c9bb5c383f44800345540ec05a67175bd7267cc
Reviewed-on: https://code.wireshark.org/review/5114
Reviewed-by: Stephen Fisher <stephenfisher@centurylink.net>