delegate: return uintptr as callback result

According to the syscall.NewCallback docs all the callbacks should
return an uintptr sized result. But we were previously using uint64
which only works for 64 bit systems. This change should allow using
winrt-go on 32 bit windows devices.

fixes #83

internal/codegen/templates/delegate.tmpl

@@ -5,7 +5,7 @@ const Signature{{.Name}} string = "{{.Signature}}"
 type {{.Name}} struct {
 	ole.IUnknown
 	sync.Mutex
-	refs uint64
+	refs uintptr
 	IID  ole.GUID
 }
 
@@ -70,15 +70,15 @@ func (r *{{.Name}}) GetIID() *ole.GUID {
 }
 
 // addRef increments the reference counter by one
-func (r *{{.Name}}) addRef() uint64 {
+func (r *{{.Name}}) addRef() uintptr {
 	r.Lock()
 	defer r.Unlock()
 	r.refs++
 	return r.refs
 }
 
 // removeRef decrements the reference counter by one. If it was already zero, it will just return zero.
-func (r *{{.Name}}) removeRef() uint64 {
+func (r *{{.Name}}) removeRef() uintptr {
 	r.Lock()
 	defer r.Unlock()
 
@@ -112,11 +112,11 @@ func (instance *{{.Name}}) Invoke(instancePtr, rawArgs0, rawArgs1, rawArgs2, raw
 	return ole.S_OK
 }
 
-func (instance *{{.Name}}) AddRef() uint64 {
+func (instance *{{.Name}}) AddRef() uintptr {
 	return instance.addRef()
 }
 
-func (instance *{{.Name}}) Release() uint64 {
+func (instance *{{.Name}}) Release() uintptr {
 	rem := instance.removeRef()
 	if rem == 0 {
 		// We're done.

internal/delegate/delegate.go

@@ -24,8 +24,8 @@ var (
 type Delegate interface {
 	GetIID() *ole.GUID
 	Invoke(instancePtr, rawArgs0, rawArgs1, rawArgs2, rawArgs3, rawArgs4, rawArgs5, rawArgs6, rawArgs7, rawArgs8 unsafe.Pointer) uintptr
-	AddRef() uint64
-	Release() uint64
+	AddRef() uintptr
+	Release() uintptr
 }
 
 // Callbacks contains the syscalls registered on Windows.
@@ -113,7 +113,7 @@ func invoke(instancePtr, rawArgs0, rawArgs1, rawArgs2, rawArgs3, rawArgs4, rawAr
 	return instance.Invoke(instancePtr, rawArgs0, rawArgs1, rawArgs2, rawArgs3, rawArgs4, rawArgs5, rawArgs6, rawArgs7, rawArgs8)
 }
 
-func addRef(instancePtr unsafe.Pointer) uint64 {
+func addRef(instancePtr unsafe.Pointer) uintptr {
 	instance, ok := getInstance(instancePtr)
 	if !ok {
 		// instance not found
@@ -123,7 +123,7 @@ func addRef(instancePtr unsafe.Pointer) uint64 {
 	return instance.AddRef()
 }
 
-func release(instancePtr unsafe.Pointer) uint64 {
+func release(instancePtr unsafe.Pointer) uintptr {
 	instance, ok := getInstance(instancePtr)
 	if !ok {
 		// instance not found