Changed how the stock objects (wx.RED, wx.RED_PEN, wx.RED_BRUSH, etc.)

Changed how the stock objects (wx.RED, wx.RED_PEN, wx.RED_BRUSH, etc.)
are initialized.  They are now created as a wrapper object that
initializes itself on first use (when an attribute of the object is
requested.)  This was needed because of similar delayed initialization
functionality that was implemented in wxWidgets, but the end result is
cleaner for wxPython as well, and allowed me to remove some ugly code
under the covers.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38802 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775