Better fix for wxSpinCtrlGeneric enabling/disabling bug in wxMSW.

Better fix for wxSpinCtrlGeneric enabling/disabling bug in wxMSW.

To really ensure that the window containing the components of wxSpinCtrlGeneric
is never enabled under MSW (as we want to avoid this to ensure that any input
always goes to its children and not the window itself, see #12045), override
DoEnable() and not Enable(). This takes care of the case when the control gets
implicitly disabled because its parent is.

Closes #13142.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70178 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775