* lib/mountlist.c (read_file_system_list): Parse /proc/self/mountinfo
directly, rather than depending on libmount, which has many
dependencies due to its dependence on libselinux, as detailed at:
http://lists.gnu.org/archive/html/bug-gnulib/2015-01/msg00063.html
Note we restrict this to __linux__ as that's probably where this
interface will remain. If ever porting, it would be best
to first pull the makedev() wrapper from coreutils to a gnulib module.
Note also we don't add a getline dependency to the mountlist module,
as all Linux versions are sufficient.