* Fixes UART detach.  Fixes #3878

* 0 is not a good holder value for pins!

* 0 is not a good holder value for pins!

* API compatibility to AVR, ESP8266, et al

* Add non-blocking HardwareSerial::read(buffer, size) extension (ESP8266 portability)

* Refactor for fewer indirect calls.

* add option to Flush() to only clear txQueue

Add the option to cause Flush() to just wait for tx data to clear the tx fifo and uart, leave the rx queue and rx fifo as is.

* support tx only flush()

* support tx only Flush()

* support txOnly for Flush()

* compatibility to Stream()

* compatibility for Stream()

* default value error

* default value error

* Update esp32-hal-uart.h

* Update esp32-hal-uart.c

* Update HardwareSerial.cpp

* sp

* correctly implement flushTxOnly()

* Expose uartStartDetectBaudrate(uart_t *) in esp32-hal-uart.h and call it from HardwareSerial::begin() if baudrate detection is requested (by passing a baudrate of 0) to solve baudrate detection problems

* Avoid a division by zero error in uartGetBaudRate()

* Add updateBaudRate to hardware serial

* remove flush

* Fix tab

* Added baudrate detection to esp32-hal-uart and HardwareSerial

* Solved compiler warning for uartResizeRxBuffer()

* Add unit to header variable name (timeout_ms)

* Reverting accidentally changed files to master

* Add small delay after baudrate detection

* TX Flow Control and Code cleanup

* Use semaphore instead of delay

TX functionality is done.

* Use single buffer and empty queue on exit

* Fix compile issues because of LwIP code relocation

* Add temporary header to fix Azure not compiling

* Fix AsyncUDP early init

* AsyncUDP Multicast fixes

* Add source mac address and rework multicast

* Allow redefinition of default pins for Serials 1 and 2

* Update IDF to 3276a13

* Update esptool.py to 2.5.0

* Fix sketches

* Fix log level in BluetoothSetial

Add functionality allowing rxBuffer of HardwareSerial to be changed in size via HardwareSerial::setRxBufferSize. (#1855)

If you develop on windows and need cr/lf files, see this:

    https://git-scm.com/book/en/v2/Customizing-Git-Git-Configuration#_formatting_and_whitespace

    Git can handle this by auto-converting CRLF line endings into LF
    when you add a file to the index, and vice versa when it checks out
    code onto your filesystem. You can turn on this functionality with
    the core.autocrlf setting. If you're on a Windows machine, set it
    to true - this converts LF endings into CRLF when you check out code:

    $ git config --global core.autocrlf true

* HardwareSerial - availableForWrite() support

* fix indentation errors (tab vs space)

Added argument to HardwareSerial.begin to specify whether the logic levels of the UART rx and tx lines should be inverted (#719)

* Print error when serial number is invalid

* Move to the first check, change end by return

usefull for ESP8266 compatibility

Fixes: https://github.com/espressif/arduino-esp32/issues/270

NOTE: UART1's default pins can be used only when SPI Flash is DIO

thanks @Ladyada

many possible problems fixed in preparation for thread-safe