wxwidgets.cfg: replace wxColor with wxColour as wxWidgets does the same their header.

cfg/wxwidgets.cfg

@@ -22,6 +22,7 @@
   <define name="wxExit" value="exit"/>
   <!-- wxVector<T> is a template class which implements most of the std::vector functions -->
   <define name="wxVector" value="std::vector"/>
+  <define name="wxColor" value="wxColour"/>
   <define name="wxOVERRIDE" value="override"/>
   <define name="wxEXPLICIT" value="explicit"/>
   <define name="wxICON(name)" value="name"/>