allow set parent on axes handle

allow set parent on axes handle

f = figure("dockable", "off", "infobar_visible", "off", "toolbar_visible", "off", "menubar_visible", "off", "backgroundcolor", [0.5 0.5 0.5]);

fr1 = uicontrol("style", "frame", "backgroundcolor", [1 0 0]);
fr1.position = [100 100 200 200];
fr2 = uicontrol("style", "frame", "backgroundcolor", [0 1 0]);
fr2.position = [300 100 200 200];
newaxes(fr1);
a = gca();
plot(1:10);

//change axes parent
//a.parent = fr2;
//a.parent = f;
//a.parent = fr1;

Change-Id: I2e3cf41a26af08458c41328729c1416da11762b2