Kernel doesn't allow to mess with map_files dir in proc. So,
when doing dump from user process, we should try to get
file path using path from smaps file. To be 100% sure the
path is correct we also get device and ino numbers and
check them agains the stat()-ed path ones.

With this scheme we miss

- mapped packet sockets, but users don't use them
- AIOs, but this can be detected via device, inode and name
- several nested mntns's, but users don't use them
- mapped and unlinked files, but this can be fixed by
  reading file via task's memory (slow, but still)

gorcunov@:

 - For special mappings such as heap, vsyscall, vdso and such
   the kernel provides names rounded by brackets so exit
   from vma_get_mapfile if we meet one and allow the caller
   to handle it.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Looks-good-to-me: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Looks-good-to-me: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>