translator: bug fix: give a tag name instead of typedef

[hajimehoshi]

Updates #174
Updates golang-ui/nuklear#91

[hajimehoshi]

This is a different approach from #150. At least this changes the compilation result of https://github.com/golang-ui/nuklear. nuklear couldn't be compiled even with this patch yet, but errors with enums were resolved.

[hajimehoshi]

Just FYI, after applying this PR, nuklear's compilation result is like this:

% go build ./nk
# github.com/golang-ui/nuklear/nk
nk/types.go:44:6: Bool redeclared in this block
        nk/const.go:47:2: other declaration of Bool
nk/types.go:70:54: Bool is not a type
nk/cgo_helpers.go:692:37: Bool is not a type
nk/cgo_helpers.go:5706:26: Bool is not a type
nk/cgo_helpers.go:6259:34: Bool is not a type
nk/cgo_helpers.go:6843:36: Bool is not a type
nk/cgo_helpers.go:6924:35: Bool is not a type
nk/nk.go:27:51: Bool is not a type
nk/nk.go:38:83: Bool is not a type
nk/nk.go:53:61: Bool is not a type
nk/nk.go:53:61: too many errors