[PATCH] cleanup mult field string handling

[PATCH] cleanup mult field string handling

Here I try to cleanup our various multifield iteration over the strings.
Inspired by our nice list.h we now have a macro to iterate over the string
and process the parts of it:
It makes the code more readable and we don't change the string while we
process it like the former strsep() does.

Example:

  foreach_strpart(dev->symlink, " ", pos, len) {
  	if (strncmp(&dev->symlink[pos], find_name, len) != 0)
  		continue;

  	...
  }

For the callout part selector %c{2} we separate now not only by space but
also newline and return characters, cause some programs may give multiline
values back. A possible RESULT match must contain wildcards for these
characters.

Also a bug in the recent udevinfo symlink query feature is fixed.