Convert array of simple structs, to C array of values

[Chris Katko]

```D
struct pair
   {
   float x;
   float y;
   }

pair[10] values;
import std.conv;
auto valuesInCStyle = to!(const float*)(values);

```

Now that's not going to work because (I would imagine) to! 
doesn't understand x, and y, can be placed in order to give an 
array of:

valuesInCStyle = [values[0].x, values[0].y, values[1].x 
,values[1].y, ...]

I know there's gotta be some simple one liner function in D, but 
I can't think of it.