Automatic whitespace cleanup. No functional change.
libroot: Accept NULL for the resolved_name argument of realpath()

as specified in IEEE Std 1003.1, 2013 Edition, see
http://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html

In this case, the returned buffer is allocated with realpath() and can be
deallocated by the caller with free().
The behavior was only "implementation defined" in previous revisions like
IEEE Std 1003.1, 2004 Edition, see
http://pubs.opengroup.org/onlinepubs/000095399/functions/realpath.html

Signed-off-by: Jérôme Duval <jerome.duval@gmail.com>