add C++ guards

include/ucore/version.h

@@ -30,6 +30,9 @@
  *  </pre>
  *  @endhtmlonly
  */
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 /* Major version of the ucore library*/
 extern const int ucore_version_major;
@@ -46,5 +49,10 @@ extern const char ucore_version_str[];
 /** Hostname where the library was built
  */
 extern const char ucore_build_host[];
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif