Fix for bz#13658 - using fsincos on x86-64

[Joseph S. Myers]

Any news here?  As noted in 
<http://sourceware.org/ml/libc-alpha/2012-02/msg00578.html> I'd like to 
see incremental progress here - some cases fixed, with testcases added, 
even if not all cases are fixed (eventually we should have reasonably 
accurate results for large arguments for all of sin, cos, sincos, tan, for 
all argument types, with associated testcases).  That would then provide a 
basis for other people to fix the long double version on top of fixes for 
other types, for example.

Given the use of sincos in other functions, having fixes for sincos is 
important to be able to add tests for large inputs to various other 
functions (in particular, fixing the Bessel function TLOSS issues).

-- 
Joseph S. Myers
joseph@codesourcery.com