MTD struct mtd_geometry_s:  Increase the size of blocksize again.  Yes, there are devices with block size greater than 64KB.

Build system: Add 'make oldconfig' target.  Use this option in tools/testbuild.sh.  Add --silent option to tools/refresh.sh so that it can be run in batch without human interaction

tools/testbuild.sh: kconfig-conf was silently failing because (1) it needs to execute from the top-level NuttX directory and (2) apps/Kconfig does not yet exist

net/: Finish IEEE802154->6LOWPAN renaming; remove PF_IEEE804154; Move 6LoWPAN menu to inside Internet Protocol Menu

drivers/wireless/ieee802154/Make.defs
    Changes to the build infrastructure to include the mrf24j40 driver

include/nuttx/spi/spi.h
    Define a IEEE SPI device

include/nuttx/wireless/ieee802154/ieee802154_radio.h
    This file defines the API of a IEEE 802.15.4 radio device, to be used by the future common MAC 802.15.4 layer

drivers/wireless/ieee802154/mrf24j40.c
drivers/wireless/ieee802154/mrf24j40.h
    The main MRF24J40 IEEE 802.15.4 radio driver

include/nuttx/wireless/ieee802154/mrf24j40.h
    This file allows instanciation of the MRF24j40 driver from board configurations

Move drivers/ieee802154 to drivers/wireless/ieee802154; rename include/nuttx/net ieee802154 to 6lowpan.h