Tiva: Updated files to allow for ADC triggering by the timer. I’ve cleaned up some parts of the ADC code, too, and fleshed out the PWM triggering ioctl.  From Calvin Maguranis

NSH: The default priority of the network initialization thread should be lower.  It is CPU intensive and can interfere with other operations

Move some useful internal logic from recvfrom.c and udp_callback.c and put them in ip.h where they can be used more generally

Move some useful internal macros from udp_send.c and put them in ip.h where they can be used more generally

Networking: Divide net_intiialize() into net_setup() and net_initialize() to solve a chicken-and-egg problem.  net_setup() must be caleld before up_initialize() is called so that networking data structures are ready to register new network devices.

net_initialize() now does only timer related operations and is called AFTER up_initialize() where the timers are configured.  This is really.

Add some inclusions of nuttx/net.h to two files.  Without these there can be compilation errors in certain configurations.  From Max Neklyudov.

Move the initialization of the networking subsystem to AFTER up_initialize is called.  Fromo Macs Neklyudov.