generated libtool.m4 should be removed from git repository

[Per Bothner]

The file tp/Texinfo/XS/gnulib/m4/libtool.m4 is is created by ./autogen.sh,
but it already exists in the git repository.  This causes 'git diff' to
show a spurious difference if the version of libtool installed is
different from that used for the checked-in version, and hence 'git pull'
may needlessly fail.

I believe the file should be removed from the repository - and added
to .gitignore.

--
        --Per Bothner
address@hidden   http://per.bothner.com/