PX4/NuttX branch test: master

NuttX:
 - https://github.com/PX4-NuttX/nuttx/tree/master
 - PX4/NuttX@9babc64

Changes from PX4/NuttX (PX4/NuttX@c6ba2c1) in current PX4/master (4f362f5)
PX4/NuttX@c6ba2c1...9babc64

9babc64438 (HEAD, origin/master) Merge branch 'master' of github.com:apache/incubator-nuttx
21ea255 net/devif/devif_poll.c:  Correct a new warning found in build testing.  devif/devif_poll.c:768:7: warning: unused variable 'hsec' [-Wunused-variable] (#97)
aa6efbd800 Merge branch 'master' of bitbucket.org:nuttx/nuttx
81651f1357 Merge branch 'master' of github.com:apache/incubator-nuttx
f005698 Fix a few errors concerning use of section block comments in .c files: (#95)
3a8241ecd0 Merge branch 'master' of github.com:apache/incubator-nuttx
f8bcd58 Fix format warn (#96)
84153ad arch/mips/src/pic32mz/pic32mz-timer.c: Eliminate a warning found during testing.
4224038c6e Merge branch 'master' of github.com:apache/incubator-nuttx
e507ca4 imxrt1050-evk/include/board.h:  Add missing definitions.  Recent i.MXRT changes added the definition IMXRT_USB1_PLL_DIV_SELECT to the imxrt1020-evk and imxrt1060-evk board.h header files but NOT to the imxrt10%0-evk.  As a result EVERY i.MXR 1050 board configuration with USB enabled failed to compile during build testing.  Another day without a successfull build test 8( (#93)

Apps:
 - https://github.com/PX4/NuttX-apps/tree/master
 - PX4/NuttX-apps@561fc02

Changes from PX4/NuttX-apps (PX4/NuttX-apps@91b6ad6) in current PX4/master (4f362f5)
PX4/NuttX-apps@91b6ad6...561fc02

561fc02a (HEAD -> master, origin/master) netutils/ftpd/ftpd.c:  Fix an error introduced in PR10.  In error clean-up, it was trying to free memory on an error where we failed allocated memory.  Not good.
e6785097 apps/netutils/ftpd/ftpd.c:  Fixes several problems:
573f07f3 fix passwd.h:103:30: warning: passwd_verify with no effect [-Wunused-value]
7fd1b906 delete all characters from char to EOL
967e7e29 system: readline: Improve security
01e2b117 system: zmodem: Improve zmodem send performance
221a4587 system: zmodem: Fix compile error in zmodem host tool
437dba33 system: zmodem: Fix debug assert condition
5c936ce0 Various fixes (#6)
74ba8ff2 Merge pull request #5 from xiaoxiang781216/fix-void-cast