Add function to set interrupt handler which save/restore alternate registers

[Arnaud6128]

Create another function identical to cpct_setInterruptHandler which also save/restore alternate registers.

In this way interruption handler can be used in same time with assembly functions that use alternate registers.

[lronaldo]

In fact, registers to be saved should be configurable. Some users may prefer a function that does not save any register.

It will be interesting to consider this.

[nestornillo]

I've converted cpct_setInterruptHandler into a configurable macro, which creates a custom version of the function that saves selected registers, opened PR #143