Added/fixed missing extern "C".

diff --git a/include/objbase.h b/include/objbase.h
index 339db84..4c46c27 100644
--- a/include/objbase.h
+++ b/include/objbase.h
@@ -26,8 +26,16 @@
 #include <stdlib.h>
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 HRESULT WINAPI GetClassFile(LPOLESTR filePathName,CLSID *pclsid);
 
+#ifdef __cplusplus
+}
+#endif
+
 
 /*    These macros are msdev's way of defining COM objects. They are provided 
  * here for use by winelib users.