This introduces a fixed precision signed 32.32 fractional type that can
work on devices without an FPU.
The integer part works as an int32_t, the fractional part represents the
fractional proportion expressed as part of 100M, so 8 fractional decimal
digit precision which is more than enough for many applications.
Add and Sub are reasonably fast as they are scaled on to a combined
uint64_t, Multiply is a little slower as it takes four uint64_t multiplies
that are summed, and divide is expensive but accurate, done bitwise taking
up to 32 iterations involving uint64_t div and mod.
