INTEGER handlers do not check for overflow

[mlazdans]

Forgot to add integer overflow check.

[mlazdans]

Fixed with: 29bc246

I added explicit integer handling and forgot to add overflow checks. The rationale was to avoid converting integers to strings and save on traffic. Before the change all integers was casted to strings. Not sure if it's worth and if the gains outweighs extra code complexity. Some benchmarks would be nice.

[MartinKoeditz]

An first sight it looks ok.
I will check the extension on my php application now.