[gfortran,ping] support for large kinds in front-end and library

[Paul Brook]

> Or, we could provide degraded functions that use the double type ones:
>
> #ifndef HAVE_ATAN2L
> long double atan2l (long double x) { return (long double) atan2 ((double)
> x); }
> #endif 

IMHO this is sufficient. If users want full support they should get their 
system vendor to provide a libm that doesn't suck quite so much.

Paul