* Simplify EINTR/ECANCEL error handling
1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx
* Unify the void cast usage
1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro
net/netlink/netlink_sockif.c: At implementation of response available signal handler needed for POLLIN logic.
net/netlink/netlink_sockif.c: Add logic to set up signal handler to receive the response notification.
So although the poll() implemenation is still not yet usable, the commit is useful because it (1) does not harm, and (2) incidentally fixes a few other issues in the NETLONK response queuing that I noted in the process.
net/netlink/netlink_route.c: Add Netlink socket NETLINK_ROUTE support for getting a snopshot of the Neighbor table.
net/neighbor/neighbor_snapshot.c: Add neighbor_snapshot() that will eventually be used by the Netlink sockets. Also fixed naming violation 'struct neighbor_entry' -> 'struct neighbor_entry_s'.
include/nuttx/net/neighbor.h: Expose format of the IPv6 neighbor table for use with Netlink sockets.
arch/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
sched/ audio/ crypto/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
Documentation/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
fs/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
graphics/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
net/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
drivers/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
include/, syscall/, wireless/: Removed all references to CONFIG_DISABLE_POLL. The standard POSIX poll() can not longer be disabled.
configs/: Remove all references to CONFIG_DISABLE_POLL. Standard POSIX poll can no longer be disabled.
Squashed commit of the following:
net/netlink: Mark netlink support as EXPERIMENTAL.
net/netlink/netlink_sockif.c: Add netlink_getpeername to the socket interface.
net: Add getpeeername() support for netlink sockets.
include/netpacket/netlink.h: Add a few more definitions and structures used at the NetLink interface. Still missing many.
net/netlink: Add basic framework for Netlink socket support.
include/: Add basic Netlink definitions.
