PX4/NuttX branch test: master

NuttX:
 - https://github.com/PX4-NuttX/nuttx/tree/master
 - PX4/NuttX@973938d

Changes from PX4/NuttX (PX4/NuttX@9331fda) in current PX4/master (fc9df31)
PX4/NuttX@9331fda...973938d

973938dc1a (HEAD, origin/master) Merge branch 'master' of bitbucket.org:nuttx/nuttx
c5e25dc259 Merge branch 'master' of github.com:apache/incubator-nuttx
9d5d60f Run all .c and .h files in last PR49 through nxstyle.
a8d63c0 various fixes (#49)
077ef70 cxd56xx improvements (#48)
c5090d3 Merge branch 'master' of github.com:apache/incubator-nuttx
1c53d2b Nxstyle checkpatch support (#47)
4ea49c5 Fix issues on fe310 including interrupt handling (#46)
926a41f bcm43xxx: correct typo error to fix build break in photon board (#45)
aad99a5 Fix typo in the file_read description (#44)

Apps:
 - https://github.com/PX4/NuttX-apps/tree/master
 - PX4/NuttX-apps@74ba8ff

Changes from PX4/NuttX-apps (PX4/NuttX-apps@91b6ad6) in current PX4/master (fc9df31)
PX4/NuttX-apps@91b6ad6...74ba8ff

74ba8ff2 (HEAD -> master, origin/master) Merge pull request #5 from xiaoxiang781216/fix-void-cast
f00b4e6f Merge pull request #4 from xiaoxiang781216/fix-suffix
85715845 Unify the void cast usage
6a65664c Application.mk remove _main suffix from REGLIST
73e1696e Merge pull request #3 from xiaoxiang781216/builtin
7a645baa Add .updated target to handle the no builtin app case correctly
8c8c4813 fix builtin_list.c:58:10: fatal error: builtin_proto.h: No such file or directory (#2)
64bc8f5b Run all .c and .h files modified in last PR through nxstyle.
49c99750 Wapi simplify (#1)
0536c5b5 apps/nshlib/nsh_parse.c:  Correct an error found in build testing.  Commit 2a462c78aa5f4ea6dc374eedd86bc85f9f79a0c4 was insufficient.  It was a mistake to revert Xiang's change of commit 9defae8af641752506d92b72ea68c8f94d24d580.  But we are on a different vector now.