add extern "C" guards; close #126

include/mruby/object.h

@@ -7,6 +7,10 @@
 #ifndef MRUBY_OBJECT_H
 #define MRUBY_OBJECT_H
 
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 #define MRUBY_OBJECT_HEADER \
   enum mrb_vtype tt:8; \
   int color:3;\
@@ -49,4 +53,9 @@ struct RObject {
 #define ROBJECT(v) ((struct RObject*)((v).value.p))
 #define ROBJECT_IVPTR(v) (((struct RObject*)((v).value.p))->iv)
 #define ROBJECT_NUMIV(v) (ROBJECT_IVPTR(v) ? ROBJECT_IVPTR(v)->size : 0)
+
+#if defined(__cplusplus)
+}  /* extern "C" { */
+#endif
+
 #endif  /* MRUBY_OBJECT_H */