cgo: improve typedef/struct/enum support

Typedefs are now Go type aliases. And C.struct_ and C.union_ prefixed
records work correctly now, even when they're not in a typedef.

testdata/cgo/main.go

@@ -9,10 +9,6 @@ import "C"
 
 import "unsafe"
 
-func (s C.myint) Int() int {
-	return int(s)
-}
-
 func main() {
 	println("fortytwo:", C.fortytwo())
 	println("add:", C.add(C.int(3), 5))
@@ -33,6 +29,10 @@ func main() {
 	cb = C.binop_t(C.mul)
 	println("callback 2:", C.doCallback(20, 30, cb))
 
+	// equivalent types
+	var goInt8 int8 = 5
+	var _ C.int8_t = goInt8
+
 	// more globals
 	println("bool:", C.globalBool, C.globalBool2 == true)
 	println("float:", C.globalFloat)
@@ -57,10 +57,14 @@ func main() {
 	C.unionSetData(5, 8, 1)
 	println("union global data:", C.globalUnion.data[0], C.globalUnion.data[1], C.globalUnion.data[2])
 	println("union field:", printUnion(C.globalUnion).f)
+	var _ C.union_joined = C.globalUnion
+
+	// elaborated type
+	p := C.struct_point{x: 3, y: 5}
+	println("struct:", p.x, p.y)
 
 	// recursive types, test using a linked list
-	lastElement := &C.list_t{n: 7, next: nil}
-	list := &C.list_t{n: 3, next: &C.struct_list_t{n: 6, next: (*C.struct_list_t)(lastElement)}}
+	list := &C.list_t{n: 3, next: &C.struct_list_t{n: 6, next: &C.list_t{n: 7, next: nil}}}
 	for list != nil {
 		println("n in chain:", list.n)
 		list = (*C.list_t)(list.next)
@@ -70,7 +74,7 @@ func main() {
 func printUnion(union C.joined_t) C.joined_t {
 	println("union local data: ", union.data[0], union.data[1], union.data[2])
 	union.s = -33
-	println("union s method:", union.s.Int(), union.data[0] == 5)
+	println("union s:", union.data[0] == -33)
 	union.f = 6.28
 	println("union f:", union.f)
 	return union

testdata/cgo/main.h

@@ -15,6 +15,11 @@ typedef struct collection {
 	unsigned char c;
 } collection_t;
 
+struct point {
+	int x;
+	int y;
+};
+
 // linked list
 typedef struct list_t {
 	int           n;

testdata/cgo/out.txt

@@ -24,9 +24,10 @@ union s: 22
 union f: +3.140000e+000
 union global data: 5 8 1
 union local data:  5 8 1
-union s method: -33 false
+union s: true
 union f: +6.280000e+000
 union field: +6.280000e+000
+struct: 3 5
 n in chain: 3
 n in chain: 6
 n in chain: 7