Remove Palm OS port.

The platform targeted by this port doesn't exist any more and the port never
achieved really working state so remove the code to avoid having to maintain
it.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70345 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/radiobut.h

@@ -25,9 +25,6 @@
            siblings trigger a hang bug in Windows (only). If this happens, add
            this style to mark the button as not belonging to a group, and
            implement the mutually-exclusive group behaviour yourself.
-    @style{wxRB_USE_CHECKBOX}
-           Use a checkbox button instead of radio button (currently supported
-           only on PalmOS).
     @endStyleTable
 
     @beginEventEmissionTable{wxCommandEvent}