patch 8.1.0105: all tab stops are the same

Problem:    All tab stops are the same.
Solution:   Add the variable tabstop feature. (Christian Brabandt,
            closes #2711)
diff --git a/src/gui_beval.c b/src/gui_beval.c
index 8c1cd96..7e46250 100644
--- a/src/gui_beval.c
+++ b/src/gui_beval.c
@@ -130,6 +130,9 @@
 	beval->msg = mesg;
 	beval->msgCB = mesgCB;
 	beval->clientData = clientData;
+#ifdef FEAT_VARTABS
+	beval->vts = NULL;
+#endif
 
 	/*
 	 * Set up event handler which will keep its eyes on the pointer,
@@ -172,6 +175,10 @@
 # else
     XtDestroyWidget(beval->balloonShell);
 # endif
+# ifdef FEAT_VARTABS
+    if (beval->vts)
+	vim_free(beval->vts);
+# endif
     vim_free(beval);
 }
 #endif