Use /proc/self/mountinfo to detect bind mounts
    
    With /etc/mtab a symlink to /proc/self/mounts, bind mount information
    can no longer be extracted from that file.
    
    2011-03-31  Miloslav Trmač  <mitr@redhat.com>
    
    	* src/bind-mount.c: Note that tmpwatch uses a related implementation.
    
    	* src/bind-mount.c (MOUNTINFO_PATH, struct mount, mount_entries)
    	(num_mount_entries, mount_data_obstack, mount_data_mark)
    	(mount_string_obstack, mount_string_mark, mount_list_obstack)
    	(mountinfo_line_obstack, init_mount_entries, read_mount_line)
    	(parse_mount_string, read_mount_entry, read_mount_entries): New
    	definitions, reading /proc/self/mountinfo.
    	(mountinfo_fd): New variable.
    	(last_path_mounted_mtime): Removed variable.
    	(add_bind_mount_path, cmp_ints, cmp_mount_entry_pointers)
    	(cmp_id_mount_entry): New functions.
    	(rebuild_bind_mount_paths, is_bind_mount, bind_mount_init): Use data
    	from /proc/self/mountinfo.