…type & 32/64-bit architectures

Depending on the machine that the rule is being run on, determine if the
result of an integer cast to len(value) will overflow e.g.

* int8, uint8, int16, uint16 (len(value)) will always overflow on 32/64-bits
* uint32(len(value)) shall overflow on 64-bit machines but not on 32-bit
* int64(len(value)) cannot overflow on 64-bit machines nor on 32-bit
* int(len(value)) cannot overflow on either 64-bit or 32-bit machines
* uint(len(value)) cannot overflow on either 64-bit or 32-bit machines

Fixes #54