the range on the higher-sized to lower-sized randomised unit tests
give input values that are so large, they're almost exclusively
converted to +INF (or hit the -ve limit - 0 for unsigned, -INF for signed)
better tests are needed.
* fcvt float2int (large FP to smaller int)
* int2float (for FP16/32/64 to FP16)
* fcvt FP to FP (large FP to smaller FP)
int input is fairly easy to deal with: test within "close" range.
FP however needs *FP* numbers to be generated that will (or will
almost) fit into the target int range.
added appx-range within chosen int (-INTMAX*2 to +INTMAX*2) now need one
that is very close to the limits.
also added floating-point conversion tests which convert numbers just at
the limits of accuracy (or INF) of the target number.