net/tcp:  In tcp_input(), add the logic to detect, decode, and respond to TCP Keep-Alive packets.  In tcp_timer(), fix some problems with the way that TCP Keep-Alive probes were being formatted.

arch/arm/src/stm32/usb: skip recipient check for descriptor related requests

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

    net/tcp:  Add logic to send probes when SO_KEEPALIVE is enabled.
    net/tcp:  TCP socket should not have to be connected to configure KeepAlive.
    net/: Add a separate configuration to enable/disable KEEPALIVE socket options.
    net/tcp: Arguments to TCP keep-alive timing functions probably should be struct timeval as are the times for other time-related socket options.
    net/tcp:  Fix a backward conditional
    net/tcp:  Add some more checks and debug output to TCP-protocol socket options.
    net/tcp:  Cosmetic changes to some alignment.
    net/:  Adds socket options needed to manage TCP-keepalive and TCP state machine logic to detect if that the remote peer is alive.  Still missing the timer poll logic to send the keep-alive probes and the state machine logic to respond to probes.

drivers/lcd/ft80x:  Fix a typo that caused the driver to fail to recognize the ft801 chip version. Also update an unrelated README file.

    drviers/lcd/ft80x:  No longer depends on CONFIG_EXPERIMENTAL
    Update README.txt

    drivers/lcd/ft80x:  ACTIVE host command appears to be formatted differently than other host commands; Fix ROM CHIPID.  Appears to be big-ending, BCD.
    drivers/lcd/ft80x:  Fix some compile issues when debug features are enabled.

drivers/net/phy_notify.c:  Use phy debug macros instead of net debug macros.  ninfo() and nerr() are used a bit too much, so the console output is difficult to read with network debug.

arch/arm/src/stm32:  While we are at it and the differences are fresh in mind, add support for the rest of the STM32F401 family.

Feature pca9540bdp i2cmultiplexer

* Implement common i2c multiplexer abstraction to be reused by i2c multiplexer devices. Provide common interface with transfer and reset calls to set up virtual i2c busses.

* Remove i2cmux_lower_half.c and headers, will be implemented by each mux driver

* Implement PCA9540BDP I2C multiplexer lower half which uses the common i2c mux abstraction

* Remove application interface and implement common i2c functions

* Remove application interface from pca driver and implement common i2c functions directly in the pca driver

* Use i2cerr

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

arch/srm/src/stm32f7:  Add CONFIG_RTC_PERIODIC support.  Also makes the RTC lowerhalf more like in STM32L4.

Per OpenGroup.org, syslog -- and, hence, nonstandard vsyslog, and debug wrappers -- does not return a value.  Rename _vsyslog to nx_vsyslog.  Use internal nx_vsyslog in the few cases where a return value is required.

stm32_hrtim: fix capture_get function, add software capture trigger, add software reset trigger, add outputs polarisation configuration

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

stm32_hrtim: fix capture_get function, add software capture trigger, add software reset trigger, add outputs polarisation configuration

Fix some errors found in build testing + clean-up some issues with last changes to remove use of printf() from within the OS.

Remove all usage of printf() from the OS.  That is not an acceptable context for the use of an application-oriented interface that depends on a task-specific file descriptor and C buffered I/O.

drivers/wireless/cc1101.c:  Fix a few things that I bungled in my review of the driver mods.  Fix the logic that was dumping register contents: printf() may not be used within the OS and the syslog and debug macros may add ornamentatino to the output.  The only real option inside the OS is to buffer the data and outputing with a single syslog write (vs. many tiny writes).

    cc1101:  Changes from review of last PR.
    remove gpio
    remove  cc1101 frame len
    remove FLAGS_RXONLY flags
    add cc1101 function
    remove some waring
    add cc1101 poll function
    add cc1101 register
    add cc1101 isr read data
    add cc1101 spi deviceId
    add cc1101 init2
    add wait cc1101 chip ready
    raw init cc1101

stm32f33xxx_adc.c: fix bug in RCC reset logic that resets ADC1 configuration when both ADC1 and ADC2 are in use

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

drivers/i2c and drivers/spi:  Fix compile if CONFIG_DISABLE_PSEUDOFS_OPERATIONS, fix bad NULL checks

stm32_hrtim: add repetition support and fix enum overflow

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

drivers/lcd:  Add FT80x controls for the case where the audio amplifier is controlled by FT80x GPIOs vs MCU gpios.

arch/arm/src/stm32f7: Backport RTC alarm setting changes from STM32L4.  Most notably this fixes RTC getting stuck issue when both alarms were used. Root cause was writing RTC ISR register contents to RTC CR register.