cgo: include all enums in the CGo Go AST

Not all enums may be used as a type anywhere, which was previously the
only way to include an enum in the AST. This commit makes sure all enums
are included.

cgo/libclang.go

@@ -255,6 +255,11 @@ func tinygo_clang_globals_visitor(c, parent C.GoCXCursor, client_data C.CXClient
 			// Parsing was successful.
 			p.constants[name] = constantInfo{expr, pos}
 		}
+	case C.CXCursor_EnumDecl:
+		// Visit all enums, because the fields may be used even when the enum
+		// type itself is not.
+		typ := C.tinygo_clang_getCursorType(c)
+		p.makeASTType(typ, pos)
 	}
 	return C.CXChildVisit_Continue
 }

cgo/testdata/types.go

@@ -38,6 +38,9 @@ typedef enum option {
 	optionF,
 	optionG,
 } option_t;
+enum unused {
+	unused1 = 5,
+};
 
 // Anonymous enum.
 typedef enum {

cgo/testdata/types.out.go

@@ -12,6 +12,7 @@ const C.optionD = -4
 const C.optionE = 10
 const C.optionF = 11
 const C.optionG = 12
+const C.unused1 = 5
 
 type C.int16_t = int16
 type C.int32_t = int32
@@ -81,3 +82,4 @@ type C.struct_type1 struct {
 }
 type C.struct_type2 struct{ _type C.int }
 type C.enum_option C.int
+type C.enum_unused C.uint