lib: Remove net_transmit() Its API was confusing, and it's no longer used anywhere.

global: Fix spelling mistakes in comments Original work by @andreasschulze and @jsoref

lib: Add net_ipport2str Converts struct ip_addr + port into either 127.0.0.1:6000 or [::1]:6000.

lib: Fixed net_str2port*() comments

lib: Created net_set_tcp_nodelay(), which enables the TCP_NODELAY socket option. This disables the TCP Nagle algorithm.

lib: net_get_ip_any[46]() to struct net_ip[46]_any Also add struct net_ip[46]_loopback.

lib: Implemented net_set_send_buffer_size() and net_set_recv_buffer_size(). These functions allow manipulating the kernel socket buffer sizes for a socket file descriptor.

Require IPv6 to build

lib: Added net_str2hostport()

lib: Added unit tests for net_is_in_network() about IPv4-mapped IPv6 addresses

Earlier in_port_t fix created problems with service listener configuration. Listeners are disabled with port=0, which was not allowed anymore.

Changed type of internet port values to in_port_t everywhere. Created special SET_IN_PORT setting type for internet port values. Created net_str2port() for parsing internet port values. Removed several atoi() invocations in the process.

lib: Added support for connecting UDP sockets.

lib: Added net_listen_full() with a flag to set SO_REUSEPORT on the socket if available.

net_ip2addr() changed to return "" instead of NULL on failure. Pretty much everything in the code assumed that it would never fail, which it normally doesn't except if the ip_addr was created for UNIX sockets.

dns: Use EAI_NONAME, not EAI_ADDRFAMILY to indicate "no addresses".

lib-dns, dns: Don't use IPv4-only error codes

Added net_gethostbyaddr() for DNS PTR lookups. This code assumes we have IPv6 capability. Perhaps we should just require it everywhere already..

net_is_in_network(): Don't assert-crash with invalid IP. It's probably better to do the check here instead of remembering for caller to do the check.

Renamed network.[ch] to net.[ch]. The function prefixes already started with net_ instead of network_. And icecap wants to use network.h for other purpose. :)