Squashed commit of the following:
net/icmp: Finishes off icmp_recvfrom().
net/icmp: Add readahead support for IPPROTO_ICMP sockets.
net/icmp: Add poll() support for IPPROTO_ICMP sockets.
net/icmp: Add a connection structure for IPPROTO_ICMP sockets.
net/icmp: Implements sendto for the IPPROTO_ICMP socket.
net/icmp: Move icmp_sendto() and icmp_recvfrom() to separate files. They are likely to be complex (when they are implemented).
net/icmp: Hook IPPROTO_ICMP sockets into network. Fix some naming collisions. Still missing basic ICMP send/receive logic.
configs: apps/system/ping current need poll() enabled.
configs: All defconfig files that use to enable low-level support must now enabled CONFIG_SYSTEM_PING.
net/icmp: Adds basic build framework to support IPPROTO_ICMP sockets.
net/: psock_recvfrom() is an internal interface and should not set the errno nor should it be a cancellation point.
net/: psock_accept() is not a cancellation point.
net/: psock_getsockopt() and psock_socket*9 are an internal interfaces and should not set the errno.
net/: psock_getsockopt() is an internal interface and should not set the errno.
net/: psock_listen() is an internal interface and should not set the errno.
net/: psock_connect(( is an internal interface and should not set the errno nor should it be a cancellation point.
net/: psock_bind() is an internal interface and should not set the errno.
net/: psock_accept() is an internal interface and should not set the errno.
User-space networking stack API allows user-space daemon to
provide TCP/IP stack implementation for NuttX network.
Main use for this is to allow use and seamless integration of
HW-provided TCP/IP stacks to NuttX.
For example, user-space daemon can translate /dev/usrsock
API requests to HW TCP/IP API requests while rest of the
user-space can access standard socket API, with socket
descriptors that can be used with NuttX system calls.
