[Chuck Walbourn (walbourn)]

x64 builds default to /Wp16 while ARM64 builds default to /Wp8, so this warning was added to highlight a potential problem in layout differences. The this PR adds the recommended padding to silence the warning.

EffectCommon.h(85): warning C5291: 'DirectX::EffectLights': deriving from the base class 'DirectX::EffectColor' can cause potential runtime issues due to an ABI bug. Recommend adding a 8-byte data member to the base class for the padding at the end of it to work around this bug.'

AlphaTestEffect.cpp(41): warning C5291: 'DirectX::DX11::AlphaTestEffect::Impl': deriving from the base class 'DirectX::EffectBase<`anonymous-namespace'::AlphaTestEffectTraits>' can cause potential runtime issues due to an ABI bug. Recommend adding a 8-byte data member to the base class for the padding at the end of it to work around this bug.