Implement the -n (nowrap) argument to wdiff(1).  With the -n argument
specified, and when a change spans two lines, the end of region
character sequence is displayed before the new line character, and the
start of region character sequence after it.

Add a test which implements change bars on the left for any changed
text:

% netwdiff -1n f1 f2 | sed -e 's/^/  /;/{+/s/^ /|/;s/{+//g;s/+}//g'

  ...
  static int
| difffile(const char *filename1, const char *filename2)
  {
  ...

(agc)