fpu_snapshot subdir should instead be a submodule?

[steveri]

NOW

• fpu_snapshot is copied manually to fftgen repo from fpu repo
• test scripts must check and override with latest fpu updates when available :(
• E.g. in test/test-regress.sh

        # See if fpu is up to date
        # TODO/FIXME this (rtl/fpu_snapshot) should really be a submodule, yes?
        clone=/tmp/fpu$$; git clone https://github.com/steveri/fpu $clone
        SAME=True; for f in $(cd $clone; \ls *.v); do
            diff {$clone,$fftgen/rtl/fpu_snapshot}/$f || SAME=
        done
        [ "$SAME" ] || echo 'WARNING rtl/lib does not match info in latest fpu repo'
        test -d /tmp/fpu$$ && /bin/rm -rf /tmp/fpu$$

BETTER?

• fpu_snapshot should instaed just be submodule fpu or something