Merge pull request #317 from mendsley/d3d11_cb_align16

D3D11 constant buffer must align ByteWidth to 16 bytes

src/renderer_d3d11.cpp

@@ -2650,7 +2650,7 @@ namespace bgfx { namespace d3d11
 		if (0 < size)
 		{
 			D3D11_BUFFER_DESC desc;
-			desc.ByteWidth = size;
+			desc.ByteWidth = (size + 0xf) & ~0xf;
 			desc.Usage = D3D11_USAGE_DEFAULT;
 			desc.BindFlags = D3D11_BIND_CONSTANT_BUFFER;
 			desc.CPUAccessFlags = 0;