Robustify text-27.15b that failed after [898c0657], on macOS with aqu…

…a only. The failure was due to TextClosestGap now correctly returning 1.0 (was erroneously 1.1 before) since the given position (15,3) is above the text area of the widget in the macOS aqua case due to -highlightthickness default value 3, which is not the case on other platforms. Since we are here, robustify text-27.15c as well.

tests/text.test

@@ -6662,7 +6662,7 @@ test text-27.15b {<<Selection>> virtual event on <<PasteSelection>> inside widge
     bind .t <<Selection>> "set ::retval <<Selection>>_fired"
     update
     set ::retval no_<<Selection>>_event_fired
-    event generate .t <<PasteSelection>> -x 15 -y 3
+    event generate .t <<PasteSelection>> -x 15 -y [lindex [.t dlineinfo 1.0] 1]
     update
     set ::retval
 } -cleanup {
@@ -6676,7 +6676,7 @@ test text-27.15c {No <<Selection>> virtual event on <<PasteSelection>> outside w
     bind .t <<Selection>> "set ::retval <<Selection>>_fired"
     update
     set ::retval no_<<Selection>>_event_fired
-    event generate .t <<PasteSelection>> -x 15 -y 80
+    event generate .t <<PasteSelection>> -x 15 -y [lindex [.t dlineinfo 2.0] 1]
     update
     set ::retval
 } -cleanup {