Add function to detect the gyro model in a 3ds

[rosaage]

This adds a function to get the gyro model as well as adding a string to sysinfo and a global int to the lua module.

The power registers and inspiration for the entire function comes from rehid:
https://github.com/hax0kartik/rehid/blob/5bfed26a1306be678fe3d6290c794e3bc529a086/source/Gyroscope.cpp#L97

Power registers were cross checked with problemkaputt.de for Gyro 0 and Gyro 1 along with adding who_am_i registers:
https://problemkaputt.de/gbatek-3ds-i2c-gyroscope-old-version.htm
https://problemkaputt.de/gbatek-3ds-i2c-gyroscope-new-version.htm

Simple lua test script: ui.echo("Your Gyro model is: "..GYROMODEL)

The code has been tested on:

• Launch model o3DS, reporting gyro 0
• n3DS (assembled 2 months after launch), reporting 1
• n3DS ll (assembled in 2016), reporting 2

[ihaveamac]

Make sure to add the constant to the lua doc.

[rosaage]

I also added it to the original gm9 scripting now along with some documentation in the lua-doc file.
I updated the numbering to start from 1 instead of 0.

I was a bit unsure about the return value, but I ended up with a number instead of a string as I don't know the name of the 3rd model and I feel it's better for the API to not change if/when the model name is figured out.