[Picolibc] What io-float-exact actually does

[R. Diez]

Hallo Keith:

Setting io-float-exact is documented as:

"controls whether the tinystdio code uses exact algorithms for printf and scanf"

However, io-float-exact appears to just map to symbol _IO_FLOAT_EXACT, and that symbol appears to only be used by test code.

That is, the "tinystdio code" does not use it to select any algorithm.

Am I missing something?

Thanks,
  rdiez