QDoc: End "This function is reentrant" with a dot

Fix \reentrant, \threadsafe output for functions.

Change-Id: I192ed48a292ccf7ffcc87b8422ba1f185d9d6629
Reviewed-by: Martin Smith <martin.smith@qt.io>

src/qdoc/generator.cpp

@@ -1533,6 +1533,7 @@ void Generator::generateThreadSafeness(const Node *node, CodeMarker *marker)
                 text << tlink;
             else
                 text << rlink;
+            text << ".";
         }
         text << Atom::ParaRight;
         break;