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

lpc43xx Ethernet:  Fix some backward logic setting full-duplex and 100mbps when autoconfiguration is disabled.  Noted by Anonymous in Issue #76