[glsl-in] Arrays as attributes do not seem to be supported

[StephanvanSchaik]

In GLSL, it is possible to specify structs and arrays as attributes (see https://www.khronos.org/opengl/wiki/Layout_Qualifier_(GLSL)), in which case they may consume multiple attribute locations for each element in the array or field in the struct. However, naga 0.6 does not seem to support them (arrays in vertex shaders, at least):

Examples are:

layout(location = 0) in vec4 in_foo[2];

layout(location = 0) out vec4 out_foo[2];