Add 64 bit signed/unsigned data types

[kersing]

When working with modern sensors like the BME680 using 64 bit maths is unavoidable. Currently using C code is the (only?) viable work-around which results in not being to simulate the code.

[Benj]

Hi Jac,

Good suggestion, though 64-bit variables worry me a bit especially on an 8-bit device

We can certainly put it on the list and have a go.

[kersing]

Hi Ben,

I understand why 64 bit variables might worry you, however wouldn't the same apply to float for those devices?