chLib/chCUDA: add stddef.h, math.h, memory.h includes for NO_CUDA builds

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
nbody: move CPU reference implementations from header into source files

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
nbody: rename SSE implementations to "SIMD" to allow for platform-specific code

Doesn't make sense to call it "SSE" if it's NEON or AltiVec for example.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
nbody: adding AltiVec SIMD implementation for Power architecture builds

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
nbody: add nbody_CPU_SIMD.h

Making SIMD optional by platform.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
nbody: move -O3 from CFLAGS to NVCCFLAGS

CFOPTIMIZE is non-nvcc specific (e.g. nvcc doesn't understand '-Os'), and we
need -some- optimization flag passed to nvcc without passing it to GCC as well.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
nbody: add -maltivec to CXXFLAGS if on PowerPC and NO_SIMD isn't set

Signed-off-by: Steven Noonan <steven@uplinklabs.net>