Partial array bounds checks removal

[bearophile]

Tim M:
>Oh now this will never fail but you can never be too sure.<

In the last thousand years humans have invented a thing named "mathematics". In certain circumstances it allows you to be certain of some things. In some part of the programs you can use this (simple) mathematics and be actually certain a certain bound will not be exceeded. Trust me, mathematics can be marvelous :-)

Bye,
bearophile