complex support routines

[Gabriel Dos Reis]

Jan Beulich:
> libstdc++'s complex header makes unconditional use of functions like
> __builtin_cabs[fl], which the compiler may (have to) expand to a
> function call to the normal (C99) function. However, not all platforms
> support this, and libmath support for all of the complex functions
> appears to have benn removed in late 2000. What I'd like to understand
> is how I'm supposed to use complex functions on a system that does not
> fully (or not at all) support C99 math/complex functionality.

I think the proper fix is to have the compiler always
emit the apropriate instructions without relying on the
target having C99 functions.  I don't have the time to
propose a patch for that right now.  However, a short-term
hack is to detect presence or absence of those and
put stubs in libmath.  But, that would be the short-term
hack for that problem.

-- Gaby