NSH library:  Add a Telnetd command.  This is needed when network initialization is deferred.  In that case, telnet daemon cannot be started until the network is finally initialized.  The telnetd command was added just for that case:  So that the telnet daemon can be started from the NSH command line after the network is configured.

ieee802154: start of scan/beacon-enabled network

Approved-by: Gregory Nutt <gnutt@nuttx.org>

examples/udp and examples/nettest: Fix some naming collisions; examples/nettest:  Fix some build issues with two targets.

system/dhcpc:  The DHCPC renew command did not build correctly due to naming problems.  Noted by Masayuki Ishikawa,

examples/nettest: Add support for both enpoints on target boards vs. one on a target and one on the host PC.

examples/nettest: Fix client/server naming confusion; add command line option to select the server address on the target; examples/udp:  Fix naming of a configuration setting

examples/nettest: Separate out network initialization so that it may, eventually, be used by both a target server and a target client.

examples/nettest:  Renaming some files to prevent name collision in libapps.a and to prepare to support target boards on both ends of the test

wireless/ieee802154: Adds option to make it easy to send large frame for testing purposes

Approved-by: Gregory Nutt <gnutt@nuttx.org>

examples/udp:  Port numbers need to be configurable to work with 6LoWPAN.  Need to bind the client socket to a port number.  This was not required before so is a apparently a change in the UDP packet dispatch logic.

examples/udp:  Change build so that both server and client can be on a target, rather than one on the target one on the host PC.

examples/udp:  Fixe registration as a built-in program; Change some naming to make room for a second target.  Current one endpoint is the target and one is the host.  This will (eventually) allow two targets to be both endpoints of the test.

examples/udp: Add configurable network device name; Add option to suppress network initialization which is not needed if started by NSH or for 6LoWPAN.

fix copy-paste typo in nsh_usbconsole.c

Approved-by: Gregory Nutt <gnutt@nuttx.org>