Make wxSpinCtrlGenericBase a wxCompositeWindow.

This takes care of propagating methods setting fonts and colours to the
subwindows automatically, so that setting font for the generic wxSpinCtrl now
works, unlike before.

Closes #14839.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72994 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/spinctlg.cpp

@@ -269,6 +269,14 @@ wxSpinCtrlGenericBase::~wxSpinCtrlGenericBase()
     wxDELETE(m_spinButton);
 }
 
+wxWindowList wxSpinCtrlGenericBase::GetCompositeWindowParts() const
+{
+    wxWindowList parts;
+    parts.push_back(m_textCtrl);
+    parts.push_back(m_spinButton);
+    return parts;
+}
+
 // ----------------------------------------------------------------------------
 // geometry
 // ----------------------------------------------------------------------------