arch/arm/src/stm32/lowputc: fix uart glitch when lowputc is enabled

Calling up_lowputc() when a character is in the shift register results
in corrupted character on stm32f1xx and stm32f205 cores.
TC status bit ensures that up_lowputc() waits for an on-going
transmission to complete before writing in TDR.

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

stm32f103-minimum: add support for DFU bootloader

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

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.