PX4/NuttX branch test: master

NuttX:
 - https://github.com/PX4-NuttX/nuttx/tree/master
 - PX4/NuttX@db2310b

Changes from PX4/NuttX (PX4/NuttX@1f2f6d8) in current PX4/master (2773fe6)
PX4/NuttX@1f2f6d8...db2310b

db2310b (HEAD, origin/master) lib_gethostbyaddrr.c edited online with Bitbucket
f33ed3c *Merged in zhoukejun/nuttx_nucleo-f767zi (pull request #838)
20e7ee5 configs/omnibusf4/README.txt:  Update README.
aa4f7c9 graphics/nxmu/nxmu_start.c:  Extend nxmu_start so that receives a display number as an argument.  This makes it possible to have multiple instances of the NX server running on boards that support multiple displays.  Also includes updates to boardctl() to accept display number paramters.
f6b9fe5 tools/nxstyle.c:  Add logic to detect a blank line following a left brace or a blank line preceding a right brace.
8be37f0 configs/omnibusf4/README.txt:  Add README file for OmnibusFS target.
c56ea62 arch/arm/src/imxrt/imxrt_clockconfig.c:  If SDRAM is actived it was only running at 40MHz.  This was becaus imxrt_clockconfig.c changed the SEMC clock divider after the DCD was configured.  This commit corrects that.
bd6b05f Update TODO and some comments.
2caf135 Merged in raiden00/nuttx_h7 (pull request #837)
ffca6ba Squashed commit of the following:

Apps:
 - https://github.com/PX4/NuttX-apps/tree/master
 - PX4/NuttX-apps@e063e93

Changes from PX4/NuttX-apps (PX4/NuttX-apps@7db2a35) in current PX4/master (2773fe6)
PX4/NuttX-apps@7db2a35...e063e93

e063e93 (HEAD -> master, origin/master) 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.
e54c456 (origin/px4_firmware_nuttx-7.28++) testing/ostest/setvbuf.c:  Fix several errors in the setvbuf() test.