Sourced from http://archive.ubuntu.com/ubuntu/pool/universe/w/wiringpi/wiringpi_2.50.orig.tar.gz

for kernels 4.8 onwards.

Some very old stuff might break.

Additional fixes for the ISR code and some tweaks here and
there. I've removed the checks for some operations that might
fail when using the gpiomem interface - which is now the default
way of doing things - if your program segfaults, then you
may need to use sudo on it.

Moved the extensions into wiringPi from gpio and made it more general purpose
more so that RTB and anything else can dymanically add devices
into wiringPi.
Changes to GPIO to updates for the SPI and I2C module loads
Added gpio unload for SPI and I2C.

Added a new way to setup SPI - by passing the mode in.

Support for the new Pi2 thing too

for the SPI code - it's mentioned in spidev.h but not used in the actual
kernel documentation example spi_test.c program )-:

delayMicrosecondsHard re-written - again.
Added a serialRead example program, and added in the okLed
to the examples too.
Updated/checked some of the GPIO/PWM code.
Added in some experimental servo and tone generating code and
and example or 2.
Tweaks to the gpio command to correctly load the I2C modules too.

Changed the gertboard code to use it
and ran more tests on he Gertboard code.