Latest commit 8791804 Feb 11, 2017 @kerolasa kerolasa committed with misc: do not use plain 0 as NULL [smatch scan]
text-utils/tailf.c:69:21: warning: Using plain integer as NULL pointer

Since many 'struct option' has used zero as NULL make them more readable in
same go by reindenting, and using named argument requirements.

Reference: https://lwn.net/Articles/93577/
Signed-off-by: Sami Kerola <kerolasa@iki.fi>