configs/:  apps/system/free has been deleted because it violates the portable POSIX OS interface.  Remove CONFIG_SYSTEM_FREE=y from all defconfig files.

RNDIS support on STM32F4Discovery

* stm32f4discovery: Add stm32_netinit.c to avoid a compilation error

* stm32f4discovery: Add rndis initialization in stm32_bringup.c

    NOTE: MAC address for the host side starts 0xaa.  This assignment
    scheme should be fixed later.

* stm32f4discovery: Add rndis configuration

    NOTE: STM32F4Discovery + DM-STF4BB

* drivers/usbdev/rndis.c: Fix some issues in rndis.c

    Introduce rndis_transmit() and change rndis_rxdispatch() to avoid
    packet corruption. Introduce max packet size for dual speed which
    is mainly used for high speed mode. Fix adjusting MTU warning
    on Linux host. Fix data corruption if a packet size excceds MTU.

    NOTE: Max packet size is not configured dynamically. This should
    be fixed in the future version.

* stm32f4discovery: Modify #ifdef condition for rndis in stm32_bringup()

* drivers/usbdev/rndis.c: Change HPWORK to ETHWORK

* drivers/usbdev/rndis.c: Merge the commit 07b98ccb

    Previous commit b09365784a was based on old rndis.c thus resulted
    in reverting the commit 07b98ccb. This change merges the commit.

    NOTE: In the commit 07b98ccb

, max packet size of bulkout was
    assumed to be 64. In this commit, priv->epbulkout->maxpacket is
    used instead.

Approved-by: Gregory Nutt <gnutt@nuttx.org>

configs/stm32l476-mdk:  Repartition bring-up logic so that it is more like other board directories.  Add support for USERLED driver.  Add bring-up initialization logic for the USERLED driver.

arch/arm/src/stm32/stm32f33xx_adc.c:  Eliminate warnings about cj_channels and j_chanlist being set but not used.

Changes from review of clock_nanosleep():  Misplaced right bracket, but return value in one failure case.

sched/signal/sig_nanosleep.c and libc/time/lib_nanosleep.c:  Implement clock_nanosleep().  nanosleep() is now reduced to a libc wrapper around clock_nanosleep().

libc:  Add support for readv() and write(). Also includes some cosmetic changes to some unrelated files.

STM32L4 serial PM interface improvements

* stm32l4_serial: pm: check rx/tx buffers for pending data in pmprepare

* stm32l4: remove adhoc PM interfaces and move serial suspend functionality behind CONFIG_PM

Approved-by: Gregory Nutt <gnutt@nuttx.org>

tools/configure.sh: This commit adds a -m option for macOS. For anyone not aware, Apple renamed OSX to macOS recently; thus the 'm' instead of 'o'. This does not change the other uses of *_OSX to macOS.

lc823450 auto LED support

* arch/arm/src/lc823450: Add auto LED for CPU activity

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

* configs/lc823450-xgevk: Add auto LED support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

Approved-by: Gregory Nutt <gnutt@nuttx.org>

drivers/usbdev/rndis.c: fix packet receiving logic.  The logic didn't take single-byte termination frames in account.

lc823450-xgevk audio support

* arch/arm/src/lc823450: Add IPL2 support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

* configs/lc823450-xgevk: Add IPL2 support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

* libc/audio: Fix compilation error in lib_buffer.c

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

* drivers/audio: Add WM8774 support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

* arch/arm/src/lc823450: Add I2S support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

* configs/lc823450-xgevk: Add WM8774 support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Add IPL2 support for LC823450

* arch/arm/src/lc823450: Add IPL2 support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

* configs/lc823450-xgevk: Add IPL2 support

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

Approved-by: Gregory Nutt <gnutt@nuttx.org>

sched/sched/sched_cpuselect.c:  For SMP, In order to find the cpu with the lowest priority thread, we have to remember the already found lowest priority.  Noted by Anonymous in Issue #75