[aarch64-port-dev ] frintz instruction in simulator

[D.Sturm]

Hi,
Since I need a frintz instruction when generating the floating point
remainder operation* I had to implement it in the simulator.

The implementation should be correct except in case of a signaling NaN
since that should throw an exception (could make a difference if someone
generates a signaling NaN manually from the integer pattern, but that seems
like an extreme edge case).


Maybe useful for the general branch too.

--Daniel