Remove support for MetroWerks CodeWarrior compiler.

This compiler doesn't exist any more and was probably unsupported even in 2.8,
let alone 2.9, so remove all the __MWERKS__ tests to simplify things.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71102 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/hashmap.h

@@ -689,8 +689,7 @@ public: \
     /* count() == 0 | 1 */ \
     size_type count( const const_key_type& key ) \
     { \
-        /* explicit cast needed to suppress CodeWarrior warnings */ \
-        return (size_type)(GetNode( key ) ? 1 : 0); \
+        return GetNode( key ) ? 1u : 0u; \
     } \
 }