rem function doesn't work

[Edwin Park]

Using the rem function results in this error:

error: 'remainder' was not declared in this scope
                          __result = obj<number>(remainder(number::to<real_t>(num), number::to<real_t>(div)));

This also means that the mod function does not work.

[Nurullah Akkaya]

Apparently avr-gcc does not implement remainder function. Replaced the call with % operator.