Generate wxEVT_COMMAND_TEXT_ENTER events for generic wxSpinCtrl.

Generate wxEVT_COMMAND_TEXT_ENTER events for generic wxSpinCtrl.

Pass wxTE_PROCESS_ENTER to wxSpinCtrlTextGeneric if it's specified for
wxSpinCtrl itself and also forward wxEVT_COMMAND_TEXT_ENTER events from it to
wxSpinCtrl itself.

This fixes lack of these events for wxSpinCtrlDouble under MSW and also lack
of them for any kind of wxSpinCtrl in the ports using generic version (notably
wxOSX).

Closes #14604.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72415 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775