Naga drops HLSL row_major qualifier for global matrices

[jimblandy]

Naga fails to emit the row_major qualifier in HLSL cbuffer declarations generated for global variables of type mat4x4<f32>.

The following WGSL input:

@group(0) @binding(0)
var<uniform> global_mat: mat4x4<f32>;

produces the following HLSL output:

cbuffer global_mat : register(b0) { float4x4 global_mat; }

Instead, it should produce:

cbuffer global_mat : register(b0) { row_major float4x4 global_mat; }

This was never noticed before because WGSL used to require that all globals have struct types, and Naga does include the row_major qualifier when emitting a struct declaration.