loader/cgo: add support for pointer types

testdata/cgo/main.c

@@ -9,3 +9,7 @@ int fortytwo() {
 int add(int a, int b) {
 	return a + b;
 }
+
+void store(int value, int *ptr) {
+	*ptr = value;
+}

testdata/cgo/main.go

@@ -17,4 +17,10 @@ func main() {
 	var y C.longlong = -(1 << 40)
 	println("longlong:", y)
 	println("global:", C.global)
+	var ptr C.intPointer
+	var n C.int = 15
+	ptr = C.intPointer(&n)
+	println("15:", *ptr)
+	C.store(25, &n)
+	println("25:", *ptr)
 }

testdata/cgo/main.h

@@ -1,3 +1,9 @@
 typedef short myint;
 int add(int a, int b);
+typedef int * intPointer;
+extern int global;
+void store(int value, int *ptr);
+
+// test duplicate definitions
+int add(int a, int b);
 extern int global;

testdata/cgo/out.txt

@@ -4,3 +4,5 @@ myint: 3 5
 myint size: 2
 longlong: -1099511627776
 global: 3
+15: 15
+25: 25