In case any source-based distributor/distribution of LFE
(e.g. Gentoo) wishes to overwrite the *FLAGS.

Signed-off-by: Maciej Barć <xgqt@gentoo.org>

So far it is only list comprehensions and tou cannot generate from
binaries. This is a bit of a test version, Binary comprehensions and
the new OTP 26 map comprehensions are on their way.

pandoc only allows a fixed set of tools for generating pdf and the old
default xelatex isn't available everywhere.

We now have 3 phases where we collect data, build new functions and
then compile the code. Also the generated __info__/1 functionis now
more Elixir compatible.

We now lift and rename these functions in one pass though we still
need to find the imported variables. Maybe in a future let the erlang
compiler handle this for us though it might result applying the
functions instead of calling them.

Also cleaned up the code a bit.

These also come from the Erlang shell.

This means that we can now do binary comprehenions in the LFE shell as
well. The documetation in the lfe_guide is now correct in how
binary comprehensions handle a mismatch in the generator.