Compound literals do not work in MSVC.

[takagi]

Situation
I changed to compile vector constructors to compound literals as (float3){ 0.0f, 0.0f, 0.0f }, not functions as make_float3( 0.0f, 0.0f. 0.0f ) in 9bb5706.

This change enables that global variable definitions and vector constructors are compiled to the same syntax, actually struct initializers for global variables and compound literals for vector constructors.

(defglobal x (float3 0.0 0.0 0.0))
=>
__device__ float3 x = (float3){ 0.0f, 0.0f, 0.0f };

and

(return (float3 0.0 0.0 0.0))
=>
return (float3){ 0.0f, 0.0f, 0.0f };

Problem
But it does not work on Windows because MSVC does not support compound literals (#70).

Solution
To fix this, we should treat initialization and construction as different concepts as C/C++ does.