[PATCH] amdgcn: Add vectorized math routines

Hello

This patch implements a set of vectorized math routines for use by the 
auto-vectorizer in GCC for the AMD GCN architecture. The implementation 
is located in libm/machine/amdgcn, and is based on the current set of 
scalar math routines in Newlib, from libm/common, libm/math and 
libm/mathfp (where the level of accuracy was deemed sufficient for our 
purposes). I have ensured that the copyright notices from the original 
were retained.

The vectorized routines make extensive use of the GCC vector extensions 
for C, some GCN-specific builtins in GCC, and a SIMD abstraction library 
located in libm/machine/amdgcn/amdgcnmach.h. As the builtins are a 
recent addition to GCC, I have added #if statements to skip compilation 
of the routines that use them to ensure that Newlib will still build for 
older versions of GCC.

Versions for 2-lane vectors up to 64-lane vectors (in powers of 2) are 
provided for all public functions. Versions with <64 lanes (which is the 
'natural' vector width for AMD GCN) are shims that call the 64-lane 
version with the unused lanes masked out.

Okay for inclusion into Newlib?

Thanks

Kwok Yeung