sched/semaphore:  Add nxsem_post() which is identical to sem_post() except that it never modifies the errno variable.  Changed all references to sem_post in the OS to nxsem_post().

    sched/semaphore:  Add nxsem_destroy() which is identical to sem_destroy() except that it never modifies the errno variable.  Changed all references to sem_destroy() in the OS to nxsem_destroy().

    libc/semaphore and sched/semaphore:  Add nxsem_getprotocol() and nxsem_setprotocola which are identical to sem_getprotocol() and set_setprotocol() except that they never modifies the errno variable.  Changed all references to sem_setprotocol in the OS to nxsem_setprotocol().  sem_getprotocol() was not used in the OS

    libc/semaphore:  Add nxsem_getvalue() which is identical to sem_getvalue() except that it never modifies the errno variable.  Changed all references to sem_getvalue in the OS to nxsem_getvalue().

    sched/semaphore:  Rename all internal private functions from sem_xyz to nxsem_xyz.  The sem_ prefix is (will be) reserved only for the application semaphore interfaces.

    libc/semaphore:  Add nxsem_init() which is identical to sem_init() except that it never modifies the errno variable.  Changed all references to sem_init in the OS to nxsem_init().

    sched/semaphore:  Rename sem_tickwait() to nxsem_tickwait() so that it is clear this is an internal OS function.

    sched/semaphoate:  Rename sem_reset() to nxsem_reset() so that it is clear this is an internal OS function.

net/: Versions of psock_send() and pock_sendto() should not set errno.  That is taken care of at a higher level in the send()/sendto() implementation as appropriate.

:Remove CONFIG_NET_6LOWPAN_FRAMELEN.  In this case where multiple radios are support3d, this may not be a constant.  6LoWPAN now always queries the driver to get the maximum frame length.

Networking:  Fix a race condition.  The accept() operation is performed with the network locked.  However, the network is unlocked BEFORE the connected state is set.  Therefore, a context switch may occur and the socket may no longer be connected when it is marked so.  Noted by Pascal Speck.

Networking:  Clean up some naming that has bothered me for a long time... There are no interrupts and no interrupt handlers in the network.  There are events and event handler (there used to to be interrupt logic in there years ago but that is long, long gone).

6LoWPAN:  The original, Contiki-based design used only a single buffer for reassemblying larger packets.  This could be a problem issue for hub configurations which really need the capability concurrently reassemble multiple incoming streams concurrently.  These was also a design issue in that the reassembly buffer could be corrupted by outgoing packets.  The design was extended to support multiple reassembly buffers, each associated with the reassembly tag and source address.  This assures that there can be be no corruption of the reassembly once it has started.

PF_IEEE802154:  Improve some backlog counting logic; add more assertions to catch cases where the backlog count might deviate from the actual backlog.

PF_IEEE802154:  Add a maximum backlog option.  This will prevent overrun of the RX frame queue if many frames are received from the radio, but no application is receiving the queued data.

PF_IEEE802154: On input, there may be a list of frames provided, not just one.  When closed() and connection is freed, also need to free any frames remaining in the RX queue.

commit 5b7b6e6e616c475c782e9883ada9f4a3b7cb4e2c
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Aug 20 11:13:17 2017 -0600

    IEEE 802.15.4 network device:  Make same changes as per loopback device so that it will build with PF_IEEE802154 but without 6LoWPAN.

commit d656a98cf8eab2f20e884224b52cd47ec35df4cc
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Aug 20 10:31:28 2017 -0600

    PF_IEEE802154: More fixes to device registration and to IEEE 802.15.4 loopback driver for PF_IEEE802154 without 6LoWPAN.

commit 866bb9cbb0c5af79734bbd434c07fa2560b6608f
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Aug 20 09:58:13 2017 -0600

    Network: Reorganize some Kconfig selections.

commit 230b4cb48008cba5fccdafa22340df1d43584829
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Aug 20 09:19:53 2017 -0600

    Changes to conditional compilation so that PF_IEEE802154 can build without 6LoWPAN

commit d96cbd6520d40590a740f695c4cd72208ce872da
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sun Aug 20 09:17:02 2017 -0600

    configs/sim/pf_ieee802154: Disable 6LoWPAN, IPv6, TCP, and UDP.  Now things do not build

6LoWPAN/PF_IEEE802154:  Created radiodev.h and renamed various structures to provide a better separation between 6LoWPAN and PF_IEEE802154.

PF_IEEE802154:  With this commit PF_IEEE802154 address family is basically functional.  More testing is needed, of course.

commit 2a3ab1652a2c95bcfc8be8380fc7cbdcb6472938
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Sat Aug 19 08:44:31 2017 -0600

    PF_IEEE802154: Finish some missing bind() logic.  Add configs/sim configuration for testing.

commit 59be4b846a6e3bfe82087a888e3fdac9c3c414e5
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Aug 18 19:30:04 2017 -0600

    PF_IEEE802154:  More renaming to decouple 6LoPAN from radios in general.

commit 69fabb1aea76e54381bdc13de28a3f1441fb42f4
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Aug 18 19:21:11 2017 -0600

    PF_IEEE802154: Missed a few renamings.

commit ff0af1bb25567720934cc1c2a721ccd92cc35f89
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Aug 18 17:46:58 2017 -0600

    PF_IEEE802154:  A few bugfixes

commit 01c7c84afd00cf907d280d30cfaf0fb2cf90e02e
Author: Gregory Nutt <gnutt@nuttx.org>
Date:   Fri Aug 18 17:01:31 2017 -0600

    PF_IEEE802154:  A few bugfixes

commit dcef4056d1c1488c93151135f3b7106977faa903
Author: Gre...