[rfc] enable non-trivial complex division

[Paolo Carlini]

Joseph S. Myers wrote:

>                                                                     That 
>suggests for now having -fcx-limited-range as a language-independent flag, 
>included in -ffast-math for all languages, which switches from the default 
>of 1 (2 for C99) to 0 (and -ffast-math -fno-cx-limited-range keeping the 
>default of 1 or 2) with C99 only changing the default from 1 to 2; and in 
>future adding logarithmic reduction for both 1 and 2.
>  
>
I concur.

Paolo.