Jit: get rid of incorrect implementations of fres and frsqrte.

The existing implementations produce answers which aren't consistent with
the hardware, and games care about correct floating point math.

These can be reimplemented at some point in the future, if someone cares
enough, but the general case is probably too much code to inline.

(I'm leaving the ARM implementations in place by request, even though they
suffer the same issues.)
Interpreter: refactor the rsqrte code, and use it for ps_rsqrte.
New frsqrte implementation; verified accurate.

This is similar to the old implementation, but it uses smaller tables, and
handles more edge cases correctly.  (hwtest coming soon.)
Jit: Use infinity and NaN from numeric_limits.

MSVC's implementation of INFINITY is unusable.
Interpreter: Code style fixes.