Truncate input values to their lengths

[veremenko-y]

Truncate input values in makeversion.c.
This prevents broken output of uname if values with exceeding length are suplied.

[EtchedPixels]

How are we getting broken lengths in the first place is my question ?

[veremenko-y]

I came across it when I tried adding timestamp to the kernel build, so I can track when last I compiled the kernel on the PI.
As of now I don't think there's any code path that hits it. Feel free to close it at your discretion.

[EtchedPixels]

Ok probably better to do something in kernel/start.c lilke

#ifdef KERNEL_PRINT_ID
kputs(KERNEL_PRINT_ID);
#endif