Add missing header

Change-Id: I4bc3f2743b2d57308e687eb37f78c625c2bdc184
Reviewed-on: https://gerrit.libreoffice.org/65364
Tested-by: Jenkins
Reviewed-by: Jens Carl <j.carl43@gmx.de>

include/test/container/xnameaccess.hxx

@@ -14,6 +14,7 @@
 
 #include <com/sun/star/uno/Reference.hxx>
 
+#include <rtl/string.hxx>
 #include <test/testdllapi.hxx>
 
 namespace apitest