cgo: add support for anonymous structs

testdata/cgo/main.go

@@ -71,9 +71,13 @@ func main() {
 	printBitfield(&C.globalBitfield)
 
 	// elaborated type
-	p := C.struct_point{x: 3, y: 5}
+	p := C.struct_point2d{x: 3, y: 5}
 	println("struct:", p.x, p.y)
 
+	// multiple anonymous structs (inside a typedef)
+	var _ C.point2d_t = C.point2d_t{x: 3, y: 5}
+	var _ C.point3d_t = C.point3d_t{x: 3, y: 5, z: 7}
+
 	// recursive types, test using a linked list
 	list := &C.list_t{n: 3, next: &C.struct_list_t{n: 6, next: &C.list_t{n: 7, next: nil}}}
 	for list != nil {

testdata/cgo/main.h

@@ -27,11 +27,22 @@ typedef struct collection {
 	unsigned char c;
 } collection_t;
 
-struct point {
+struct point2d {
 	int x;
 	int y;
 };
 
+typedef struct {
+	int x;
+	int y;
+} point2d_t;
+
+typedef struct {
+	int x;
+	int y;
+	int z;
+} point3d_t;
+
 // linked list
 typedef struct list_t {
 	int           n;