PX4-NuttX/nuttx branch test: px4-master_auto_rebase

NuttX:
 - https://github.com/PX4-NuttX/nuttx/tree/px4-master_auto_rebase
 - PX4/NuttX@77b8cbf

Changes from PX4-NuttX/nuttx (PX4/NuttX@8957a02) in current PX4/master (459ad75)
PX4/NuttX@8957a02...77b8cbf

77b8cbf (HEAD, origin/px4-master_auto_rebase) [PX4: WIP] Fix transmission status handling in the serial interrupt
f5de136 [PX4: REJECTED] cstdint fix
85d92a2 [PX4: REJECTED] add math.h
5c1c4e7 [PX4: WIP] Jenkinsfile
1185ff1 Merged loadable_app into master
679d287 Update some comments.
9b7e5ed configs/metro-m4:  Add an option to build the Metro M4 image to run out of SRAM.  This ought to be a safer and quicker way to do the initial bring-up (having bricked the first Metro M4 due to a bad FLASH image).
bbee0d7 arch/arm/src/stm32f7:  Fix an error introduced by the patch by Evgeniy Bobkov in Issue #114.  That patch brok all STM32 F7 builds.
056d704 This commit brings in a fragmentary, experimental implementation of NETLINK sockets.  There is not too much to that socket support on this initial commit, just the netlink socketer framework.  However, I decided to bring it into master because there is a enough that I would not want to lose what is in place.  And since it is dependent on CONFIG_EXPERIMENATL, its presence on master should be innocuous.
caa7fa7 This commit ports the stm32f20xxf40xx_flash.c driver to the STM32F7 platform and fixes some relevant problems in the header files.

Apps:
 - https://github.com/PX4-NuttX/apps/tree/px4-master_auto_rebase
 - PX4/NuttX-apps@4898f0a

Changes from PX4-NuttX/apps (PX4/NuttX-apps@36806ba) in current PX4/master (459ad75)
PX4/NuttX-apps@36806ba...4898f0a

4898f0a (HEAD -> px4-master_auto_rebase, origin/px4-master_auto_rebase) [REJECTED] add-var-expansion-in-nsh-parse.patch
922283e Squashed commit of the following:
3e81973 include/netutils/netlib.h:  Eliminate a warning about AF_UNSPEC and AF_INET not defined.
a1e5bf6 apps/system/i2c:  Adapt to rename I2C_M_RESTART->i2C_M_START.  I2C_M_NOSTOP should be in flags of first message in every write-read and write-write mesage sequence.
d9cb917 Merged in masayuki2009/nuttx.apps/refactor_nxplayer (pull request #149)
822291b apps/fsutils/mkfatfs:  Add some comments.  Clean up some coding style issues.
d365707 Add definitions for the FAT boot record (FBR).
6916fa0 fs/fat:  Clean up some name BS_ and MBR_ refer to the same record and should use the same naming (MBR_).
f0b4f14 Eliminate some new warnings reported in build testing.
3cc79be examples/lvgldemo/ and graphics/littlevgl/:  pdate LVGL to version 5.1.1