Move the remaining files from include/nuttx/net/uip to include/nuttx/net; Rename *_internal.h header files in net/ to just *.h

SAMA5D4:  More progress on XDMAC driver (still no complete); Also fixes some critical errors in the SAMA5D3 DMA definitions

Move include/nuttx/net/uip/uip-arch.h to include/nuttx/net/arp.h; rename all uip_arp_ functions to arp_

Move include/nuttx/net/uip/uip-arch.h to include/nuttx/net/arp.h; rename all uip_arp_ functions to arp_

snprintf():  If size is zero, then snprintf() should return the size of the required buffer without writing anyting.  From Sami Pelkonen

Move prun from interpreters/ to system/;  And an NSH built-in appliation that can be used to execute P-Code files from the NSH command line

Create P-Code execution helper in apps/interpreters/prun; The P-Code binary format is functional except that there are still some modularity and kernel build issues that need to be addressed.

P-code BINFMT:  Add logic to pass information from the binfmt logic to the P-code interpreter.  This includes some extension to the binfmt interfaces.

Update the displayed I2C on each get iteraction (not the same starting address).  From Ryan VanSickle