libstdc++-v3 configury problem

[Jakub Jelinek]

Hi!

Several GCC targets provide long double != double support which depends on
a compiler switch.
Unfortunately, this clashes with libstdc++-v3 determining the availability
/non-availability of math *l functions at configure time.
Depending on -mlong-double-{64,128}, -m{32,64} or how is the option called on a
particular arch, it may be or may be not available in headers.
E.g. sparc64-linux has most of the *l functions for 64-bit programs, for
32-bit programs it doesn't unless -mlong-double-128 is used.

	Jakub