PX4/NuttX branch test: master

NuttX:
 - https://github.com/PX4-NuttX/nuttx/tree/master
 - PX4/NuttX@4802eb6

Changes from PX4/NuttX (PX4/NuttX@1f2f6d8) in current PX4/master (2ae2331)
PX4/NuttX@1f2f6d8...4802eb6

4802eb6 (HEAD, origin/master) tools/nxstyle.c:  Fix a bacward test in the previous commit.
ba859ad tools/nxstyle.c:  Don't complain about certain lowercase characters in otherwise uppercase pre-processor identifers:  IPv6, IPv4, ICMPv6, IGMPv2, p as a decimal point, d signifying a divisor.  It was a bad idea to let the door open a crack for there.  While they improve readability, the inconsistently also causes other problems.
82b276a binfmt/nxflat.c:  Trivial design simplification.
622202d binfmt/nxflat.c: Update to last NxFLAT change:  The logic must respect the reference count before freeing the dspace memory region.
ba8714d binfmt/nxflat.c:  Correct a double free debug assertion.  This occurs when groups are enabled:  (1) once via binfmt_exit and unload_module, and (2) once via sched_releasetcb().  this was corrected by adding logic to free/unload the memory once and nullify the pointer so that cannot be freed a second time.  This commit resolves Bitbucket issue #145.
043df95 arch/arm/include/nrf52/ and arch/arm/src/nrf52:  1. Added 52840 family support 2. Use common irq and memory layout header file for 52832 & 52840.
f6b00e1 tools/nxstyle.c:  Fix logic error that prevent detecion of '/' and '/=' as operators.  net/:  Minor updates resulting from testing tools/nxstyle.
0a7f764 Merged in raiden00/nuttx_h7 (pull request #839)
db2310b lib_gethostbyaddrr.c edited online with Bitbucket
f33ed3c *Merged in zhoukejun/nuttx_nucleo-f767zi (pull request #838)

Apps:
 - https://github.com/PX4/NuttX-apps/tree/master
 - PX4/NuttX-apps@520bd6a

Changes from PX4/NuttX-apps (PX4/NuttX-apps@7db2a35) in current PX4/master (2ae2331)
PX4/NuttX-apps@7db2a35...520bd6a

520bd6a (HEAD -> master, origin/master) Merged in zhoukejun/apps_nucleo_f767zi (pull request #171)
e063e93 apps/examples/nxterm:  NxWM passed the size of the NxTK sub-window but nxterm example passed the size of the complete NxTK window.  They must be made consistent.
66af5b4 apps/Nxwidgets:  Fix some recently introduced errors found in build testing.
e4e00f7 apps/examples/sx127x_demo/Kconfig:  Fix misplaced 'if'
c019c9d apps/examples/modbusmaster/mbmaster_main.c:  eMBMasterRegHoldingCB cannot be static.
53e6f4b apps/examples/nxterm, graphics/NxWidgets:  Replace illegal direct calls to nxterm_redraw() and nxterm_kbdin() with new boardctl() calls.
6529a84 apps/examples/nxterm:  Most configuration options were not available in the Kconfig file.
c341abf graphics/NxWidgets/nxwm/src/cnxterm.cxx:  Part of the last change was still in he editor.
061b433 apps/examples/nxterm and graphics/NxWidgets/nxwm:  Replace direct calls to nxtk_register with legal, indirect calls via boardctrl(BOARDIOC_NXTERM).  Replace calls to (deleted) nxterm_unregister().  The correc way to delete a driver is by unlink'ing it.
2eaf2e0 (origin/px4_firmware_nuttx-7.28+_rt) aps/system/cu/Kconfig:  CU term depends on TERMIOS and should select it.