merge: Remove noise from --show-wiggles output.

merge: Remove noise from --show-wiggles output.

When --show-wiggles is used with whole files (current, orig, new) and
extraneous text in orig/new (Which isn't a change, so should be
ignored) is treated as a wiggle and causes a conflict to be shown.
Obviously not good.

So insist that any show-wiggle conflict contains at leas a Changed or
a Conflict.  Also allow Changed and Unmatched to be 'near' each other,
not only on the same line, to signal a wiggle.  Current 'near' measure
is 3 lines.

Signed-off-by: NeilBrown <neilb@suse.de>