Change f32x3 to union

src/vec/vec.h

@@ -31,9 +31,8 @@ struct f32x2 {
   };
 };
 
-typedef struct f32x3 V3f;
-struct f32x3 {
-  union {
+typedef union f32x3 V3f;
+union f32x3 {
   f32 elements[V3_ELEM_COUNT];
   struct {
     union {
@@ -49,7 +48,6 @@ struct f32x3 {
       f32 b;
     };
   };
-  };
 };
 
 typedef struct f32x4 V4f;