HPCC-10525 Solve constant folding functions for ARM

ARM32 implementation - tested in isolation but not in the context of the
compiler, as I don't have a suitable machine.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
But the registers are 4 bytes...

I suspect it should say 4 BUT there may need to be different code once you run out of registers OR code to ensure that the number of parameters is rounded up to an even number. I will experiment.