Remove entab and associated detritus.
We don't need this anymore, because pg_bsd_indent has been taught to
follow the same tab-vs-space rules that entab used to enforce.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.
1495162840@sss.pgh.pa.us