route/cls: support 'match mark' u32 filters

Signed-off-by: Thomas Haller <thaller@redhat.com>
route/cls: minor fixes in for match mark filters

- whitespace
- fix newline and whitespace in output of u32_dump_details()
- let rtnl_u32_del_mark() clear U32_ATTR_MARK

Signed-off-by: Thomas Haller <thaller@redhat.com>
route/cls: merge branch 'route-cls-u32-match-mark'

http://lists.infradead.org/pipermail/libnl/2014-November/001699.html

Signed-off-by: Thomas Haller <thaller@redhat.com>