Array of array: Implement the core functionality: types, constructors, operations.

There will be subsequent commits to refine semantics, esp. version-specific semantics,
as well as I/O functionality and restrictions.

Note: I'm getting white-space differences in the preprocessor test results,
which I'm not checking in.  I think they need to be tagged as binary or something.

Test/specExamples.vert

@@ -20,7 +20,7 @@ uniform Transform {  // API uses
 
 layout(location = 3) in vec4 normal;
 layout(location = 6) in vec4 colors[3];
-layout(location = 9) in mat4 transforms[2];
+layout(location = 9) in mat4 transforms2[2];
 
 layout(location = 3) struct S {
     vec3 a1;