wxMSW wxSlider implementation stored the min and max labels widths as fields of wxSlider object for some reason even though they were only used in one of its methods (and can be easily computed anyhow). Make them simple local variables instead and also rename an existing local variable which started conflicting with their new names. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68229 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775