Provide means for easy 16-alignment and std::vector embedding.

[juj]

Data structures need to be aligned to 16 bytes for efficient SIMD loads and stores.
Also, data structures are often desired to be emdedded inside std::vectors.

If the data structure has declspec(align) members, it cannot be embedded into a std::vector.

As a workaround, provide something like the following scheme:

class float4_unaligned
{
float x,y,z,w;
__m128 sse;
};

typedef __declspec(align (16)) float4_unaligned float4;

// Use case 1 on the stack:
float4 x; // Will be aligned.

// Use case 2 in a vector:
vector<float4_unaligned, custom_16_aligned_allocator> vectorOfFloats; // Will be aligned. See aligned allocator here http://www.velocityreviews.com/forums/t646180-make-stl-containers-allocate-aligned-memory.html
vector<float4_unaligned> vectorOfFloats; // Wouldn't be aligned, and crash at runtime.
vector vectorOfFloats; // Wouldn't probably compile due to http://stackoverflow.com/questions/1281415/error-c2719-val-formal-parameter-with-declspecalign16-wont-be-alig