Fold in SIMD support from SRE library

Fold in the SIMD support files from the SRE library, providing an
extensive set of (in principle) platform-independent primitives for
128-bit wide SIMD operations as well as specific implementation for
things like dot products and matrix multiplications.

At the moment, SIMD functions are only implemented for the x86/x86-64
platforms with SSE2/SSE3.

Rename random.cpp to dstRandom.cpp and rename rng-cmwc.cpp to
dstRNGCMWC.cpp.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>