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>

Switches IEEE 802.15.4 based code to using byte arrays instead of uint16_t values for short address and PAN ID

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