* I2C driver speed-up, i2c.SLOW, i2c.FAST and user-defined speed selection
* - Multiple buses (up to 10) with different speeds on each bus
- Standard(Slow, 100kHz), Fast(400kHz) and FastPlus(1MHz) modes or an
arbitrary clock speed
- Sharing SDA line over multiple I²C buses to save available pins
- GPIO16 pin can be used as SCL pin, but it does not support clock
stretching and selected bus will be limited to FAST speed.
* Dynamic memory allocation, error checks, simplification, timing tweaks.
* Separated the code of old driver for better compatibility and simplicity
* Change of driver interface
* Add bus status check in setup(); simplify getDC(); remove unnesessary lines in ACK read/write
* Fix for moved doc file and trailing whitespaces
* Update TLS protocol support
TLS1.0 is past PCI's EOL; BEAST is no more
Enable elliptic curve key exchanges
Do not enable the smallest ECs for security
Do not enable the largest ECs for computational time
Do not enable 25519 (sad) because it doesn't go across the wire
Drop non-PFS key exchanges
Drop ARC4, Blowfish, DES, genprime, XTEA code
Drop renegotiation support completely
It takes so much heap that it's not likely to work out well
Tidy handling of SSL_BUFFER_SIZE
Update docs
Drop mention of startcom, since they are no more, for letsencrypt
* Update mbedtls to 2.7.7
Preserve our vsnprintf and platform hacks
* Introduce TLS maximum fragment size knob
Reduce buffer size to 4Ki by default and advertize that. That's the
largest we can advertize with the TLS MFL extension, so there's no
point in making them larger. The truly adventurous can re-raise
SSL_BUFFER_SIZE and undefine the SSL_MAX_FRAGMENT_LENGTH_CODE and get
back to the earlier behavior.
* Default to mbedTLS debug with DEVELOP_VERSION