diff: implement flag -B (Ignore changes whose lines are all blank)

diff: implement flag -B (Ignore changes whose lines are all blank)

>>From 7c3ce93213590bd0592435dc27d1272d0fd3309b Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov@gmail.com>
Date: Mon, 18 Jan 2010 15:52:31 -0200
Subject: [PATCH] diff: implement flag -B (Ignore changes whose lines are all blank)

function                                             old     new   delta
diffreg                                             1196    1240     +44
.rodata                                             6538    6561     +23
packed_usage                                         457     478     +21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 88/0)               Total: 88 bytes
   text	   data	    bss	    dec	    hex	filename
  70123	    733	   8576	  79432	  13648	busybox_old
  70190	    733	   8576	  79499	  1368b	busybox_unstripped

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>