examples: set attr table
examples: fix trivial error message
examples: use mnl_nlmsg_get_payload()

not increment (nlmsghdr) pointer
document: mnl_socket_open

fix return value on error
attr: validate MNL_TYPE_MSEC same as MNL_TYPE_U64
headers: update netlink.h to 3.12

To implement mmaped netlink socket.
mmap: initial
examples: for mmap

add some of original
batch: introduct mnl_nlmsg_batch_reset_buffer()

for mmap.